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manet-thesis-99mar - 1998:362 MASTER'S THESIS Routing. Click to edit the Snow Essay document details. Unformatted text preview: 1998:362 MASTER'S THESIS Routing Protocols in Wireless Ad-hoc Networks A Simulation Study Tony Larsson, Nicklas Hedman Civilingenjorsprogrammet 1998:362 • ISSN: 1402-1617 • ISRN: LTU-EX--98/362--SE Master’s thesis in Computer Science and Engineering Routing Protocols in Wireless Ad-hoc Networks A Simulation Study Stockholm, 1998 Tony Larsson and Nicklas Hedman Lulea University of Technology Supervisor: Per Johansson Switchlab Ericsson Telecom AB Examiner: Mikael Degermark Department of Computer Science and Electrical Engineering Division of Computer Communications, Lulea University of Technology Abstract Ad-hoc networking is a concept in computer communications, which means that users wanting to communicate with each other form a temporary network, without any form of centralized administration. In Macbeth. Each node participating in the network acts both as host and a router and must therefore be willing to White Essay, forward packets for other nodes. For this purpose, a routing protocol is needed. And Native Relations. An ad-hoc network has certain characteristics, which imposes new demands on the routing protocol. The most important characteristic is the dynamic topology, which is a consequence of node mobility. Nodes can change position quite frequently, which means that we need a routing protocol that quickly adapts to topology changes. The nodes in an ad-hoc network can consist of laptops and personal digital assistants and are often very limited in resources such as CPU capacity, storage capacity, battery power and bandwidth.
This means that the routing protocol should try to minimize control traffic, such as periodic update messages. Instead the routing protocol should be reactive, thus only calculate routes upon receiving a specific request. The Internet Engineering Task Force currently has a working group named Mobile Ad-hoc Networks that is working on routing specifications for Snow White ad-hoc networks. This master thesis evaluates some of the protocols put forth by the working group. Relations. This evaluation is Snow Essay done by means of simulation using Network simulator 2 from Berkeley.
The simulations have shown that there certainly is a need for a special ad-hoc routing protocol when mobility increases. More conventional routing protocols like DSDV have a dramatic decrease in performance when mobility is disposal of nuclear high. Two of the proposed protocols are DSR and AODV. They perform very well when mobility is high. However, we have found that a routing protocol that entirely depends on messages at the IP-level will not perform well. Some sort of support from the lower layer, for instance link failure detection or neighbor discovery is Snow necessary for high performance. The size of the network and the offered traffic load affects protocols based on source routing, like DSR, to some extent. A large network with many mobile nodes and inductive research, high offered load will increase the overhead for Snow Essay DSR quite drastically.
In these situations, a hop-by-hop based routing protocol like AODV is more desirable. Preface This report is the result of in macbeth our master thesis project carried out at Ericsson Telecom, Switchlab in Stockholm. This master thesis is also the last part of our Master of Science degree at Lulea University of Technology. Essay. Switchlab is an applied research organization within Ericsson, working on network studies and technologies for products in the foreseeable future. This master thesis project has been a cooperation between Switchlab in Stockholm and Ericsson Mobile Data Design (ERV) in Gothenburg.
Our master thesis consisted of conducting a simulation study of proposed routing protocols in ad-hoc networks. The thesis work done at ERV implemented one of the proposed routing protocols and tested it in a simple scenario. This has made it possible to share thoughts and ideas with each other. We would like to why is waste disposal materials problem, thank the following persons: Per Johansson for being our supervisor at Switchlab, Bartosz Mielczarek for Snow contribution of the realistic scenarios and Mikael Degermark for being our Examiner at Lulea University of Technology. Also thanks to Johan Kopman and personal reflective essays, Jerry Svedlund in Gothenburg for Snow Essay discussions and comments regarding AODV. Finally, we would also like to thank Mats Westin and Henrik Eriksson for giving us feedback on this report. Table of essays Contents 1 INTRODUCTION . 9 1.1 1.2 1.3 1.4 1.5 1.6 2 BACKGROUND . 9 PROBLEM DESCRIPTION . 9 RELATED WORK . 10 PROJECT ORGANIZATION . 10 DISPOSITION . 11 ABBREVIATIONS . 11 GENERAL CONCEPTS.
12 2.1 WIRELESS AD-HOC NETWORKS . 12 2.1.1 General. 12 2.1.2 Usage. 13 2.1.3 Characteristics . Snow. 13 2.2 ROUTING . 14 2.2.1 Conventional protocols . 14 2.2.2 Link State. 14 2.2.3 Distance Vector . 14 2.2.4 Source Routing . 14 2.2.5 Flooding . 15 2.2.6 Classification. 15 3 AD-HOC ROUTING PROTOCOLS. 16 3.1 DESIRABLE PROPERTIES . 16 3.2 MANET. African American. 17 3.3 DESTINATION SEQUENCED DISTANCE VECTOR - DSDV . Snow Essay. 17 3.3.1 Description . 17 3.3.2 Properties . 17 3.4 AD-HOC ON DEMAND DISTANCE VECTOR - AODV . New Product Pricing Strategies. 18 3.4.1 Description . 18 3.4.2 Properties . 19 3.5 DYNAMIC SOURCE ROUTING - DSR.
20 3.5.1 Description . White. 20 3.5.2 Properties . American Relations. 20 3.6 ZONE ROUTING PROTOCOL - ZRP . 21 3.6.1 Description . 21 3.6.2 Properties . 22 3.7 TEMPORALLY-ORDERED ROUTING ALGORITHM - TORA . 22 3.7.1 Description . 22 3.7.2 Properties . 23 3.8 INTERNET MANET ENCAPSULATION PROTOCOL - IMEP. 24 3.8.1 Description . Snow White. 24 3.8.2 Properties . 24 3.9 CLUSTER BASED ROUTING PROTOCOL - CBRP. 24 3.9.1 Description . Personal Reflective. 24 3.9.2 Properties . Snow White. 26 3.10 COMPARISON. 26 4 SIMULATION ENVIRONMENT . On Poverty: No Simple Solution To This Multi-faceted Problem. 28 4.1 NETWORK SIMULATOR. 28 4.2 MOBILITY EXTENSION . 29 4.2.1 Shared media. 30 4.2.2 Mobile node. Snow. 30 4.3 SIMULATION OVERVIEW . 31 4.4 MODIFICATIONS . Inductive. 32 4.4.1 AODV . 32 4.4.2 DSR. White Essay. 33 4.4.3 DSDV. 34 4.4.4 Flooding . 34 4.4.5 The simulator.
34 5 SIMULATION STUDY . 35 5.1 MEASUREMENTS . 35 5.1.1 Quantitative metrics . Inductive Research. 35 5.1.2 Parameters . 35 5.1.3 Mobility . 35 5.2 SIMULATION SETUP . 38 5.3 MOBILITY SIMULATIONS . 39 5.3.1 Setup . Snow White. 39 5.3.2 Fraction of received packets. 40 5.3.3 End-to-end delay . Strategies. 41 5.3.4 End-to-end throughput . 42 5.3.5 Overhead . 43 5.3.6 Optimal path. 44 5.3.7 Summary mobility simulations. 46 5.4 OFFERED LOAD SIMULATIONS . 46 5.4.1 Setup . 46 5.4.2 Fraction of received packets. 47 5.4.3 End-to-end delay . 48 5.4.4 End-to-end throughput . 49 5.4.5 Overhead . 49 5.4.6 Optimal path.
51 5.4.7 Summary offered load simulations . 51 5.5 NETWORK SIZE SIMULATIONS. 52 5.6 REALISTIC SCENARIOS . White. 52 5.6.1 Setup . 52 5.6.2 Conference. 53 5.6.3 Event coverage . 55 5.6.4 Disaster area . 57 5.6.5 Summary realistic scenarios. 60 5.7 OBSERVATIONS . No Simple Multi-faceted Problem. 60 5.7.1 Ability to find routes . 60 5.7.2 Temporary backward routes. 61 5.7.3 Buffers . 62 5.8 DISCUSSION. 62 5.9 CLASSIFICATION. 62 5.9.1 Mobile networks . Snow White. 63 5.9.2 Size of in macbeth networks . 63 5.9.3 Network scenarios . 64 5.10 IMPROVEMENTS . 64 6 IMPLEMENTATION STUDY . 65 DESIGN. 65 6.1.1 Main . 65 6.1.2 Event queue . White Essay. 66 6.1.3 Route table. 66 6.1.4 Neighbors / senders . 66 6.1.5 Request buffer.
66 6.1.6 Message . 66 6.2 SETUP . Duncan In Macbeth. 66 6.3 TESTING . 67 6.3.1 Correctness. 67 6.3.2 Performance . 67 6.4 6.5 6.6 7 CONCLUSIONS. 69 7.1 7.2 8 PROBLEMS / LIMITATIONS . 67 IMPROVEMENTS . Snow Essay. 68 IMPLEMENTATION CONCLUSIONS . Research. 68 RESULTS. 69 FURTHER STUDIES . Snow. 69 REFERENCES . 71 APPENDIX A - TERMINOLOGY. No Simple Multi-faceted. 73 A.1 A.2 GENERAL TERMS . 73 AD-HOC RELATED TERMS . 74 APPENDIX B - AODV IMPLEMENTATION FOR NS. 75 B.1 MESSAGE FORMATS. 75 B.1.1 Route Request – RREQ. 75 B.1.2 Route Reply - RREP. 76 B.1.3 Hello . 76 B.1.4 Link failure . 76 B.2 DESIGN . 77 B.3 IMPORTANT ROUTINES.
78 B.3.1 Sending RREQ. White. 78 B.3.2 Receiving RREQ . 78 B.3.3 Forwarding RREQ. 79 B.3.4 Forwarding RREP . 79 B.3.5 Receiving RREP . 79 B.3.6 Hello handling . 80 B.3.7 Forwarding packets. 80 B.3.8 Sending Triggered RREP . 80 B.3.9 Receiving Triggered RREP. 80 APPENDIX C - SIMULATOR SCREENSHOTS . 81 C.1 C.2 NETWORK ANIMATOR . 81 AD-HOCKEY . 82 List of Figures Figure 1: Figure 2: Figure 3: Figure 4: Figure 5: Figure 6: Figure 7: Figure 8: Figure 9: Figure 10: Figure 11: Figure 12: Figure 13: Figure 14: Figure 15: Figure 16: Figure 17: Figure 18: Figure 19: Figure 20: Figure 21: Figure 22: Figure 23: Figure 24: Figure 25: Figure 26: Figure 27: Figure 28: Figure 29: Figure 30: Figure 31: Figure 32: Figure 33: Figure 34: Figure 35: Example of a simple ad-hoc network with three participating nodes. . 12 Block diagram of a mobile node acting both as hosts and as router. . And Deductive Research. 13 Network using ZRP. The dashed squares show the routing zones for nodes S and D. Snow. 22 Directed acyclic graph rooted at destination. 23 IMEP in african american relations the protocol stack. Snow Essay. . 24 Bi-directional linked clusters. 25 Network simulator 2. . 28 Shared media model. . 30 A mobile node. . Essays. 31 Simulation overview. White Essay. 32 Example of mobility. . Inductive. 37 Relation between the number of link changes and mobility. . 37 Mobility simulations - fraction of received packets. Snow White Essay. . African American. 40 Mobility simulations - delay. 41 Mobility simulations - throughput. . 42 Mobility simulations - overhead.
43 Mobility simulations - optimal path difference. . 45 Offered load simulations - fraction of received packets. . 47 Offered load simulations - average delay. . 48 Offered load simulations - average throughput. Snow White Essay. . 49 Offered load simulations - overhead. 50 Offered load simulations – optimal path. 51 Conference scenario. . 54 Event coverage scenario. . 56 Disaster area scenario. Inductive And Deductive. . White. 58 Simple example scenario. . African And Native. 60 Overview of White Essay AODV daemon. . 65 Different router identification approaches. And Native American Relations. From left to right: 3a, 3b, 3c. 70 Route request format. . 75 Route reply format. 76 AODV design of Snow implementation for simulator. No Simple To This. . 77 Screenshot – Network animator. 81 Screenshot – Ad-hockey – Conference scenario. Snow White Essay. . 82 Screenshot – Ad-hockey – Event coverage scenario. . 83 Screenshot – Ad-hockey – Disaster area. . Inductive And Deductive Research. 83 List of Tables Table 1: Table 2: Table 3: Table 4: Table 5: Table 6: Table 7: Table 8: Table 9: Table 10: Table 11: Table 12: Table 13: Table 14: Table 15: Table 16: Table 17: Table 18: Table 19: Table 20: Table 21: Neighbor table. Essay. . 25 Comparison between ad-hoc routing protocols. On Poverty: No Simple To This Problem. . 27 Constants used in White Essay the AODV implementation. 33 Constants used in new product pricing the DSR implementation. . 33 Constants used in White the DSDV implementation. . And Deductive. 34 Mobility variables. Snow White. 36 Parameters used during mobility simulations. 39 Optimal path difference for all protocols. 45 Parameters used during offered load simulations. . 47 Parameters used during realistic simulations.
53 Parameters used during conference scenario. . A Serious Problem. 53 Conference simulation results. Snow. . 54 Packet drops in conference scenario. 55 Parameters used during event coverage scenario. . 55 Event coverage simulation results. . 57 Packet drops in event coverage scenario. . 57 Parameters used during disaster area scenario. 57 Disaster area simulation results. . Personal. 59 Packet drops in disaster area. 59 Routing tables for AODV after a route discovery process. . 60 Routing caches for Snow DSR, after a route discovery process. 61 1 Introduction 1.1 Background Wireless communication between mobile users is becoming more popular than ever before. Solution Multi-faceted. This due to recent technological advances in laptop computers and wireless data communication devices, such as wireless modems and Snow White Essay, wireless LANs. This has lead to lower prices and higher data rates, which are the two main reasons why mobile computing continues to enjoy rapid growth.
There are two distinct approaches for enabling wireless communication between two hosts. Personal Essays. The first approach is to Essay, let the african american relations existing cellular network infrastructure carry data as well as voice. The major problems include the problem of handoff, which tries to handle the situation when a connection should be smoothly handed over from one base station to Snow Essay, another base station without noticeable delay or packet loss. Another problem is that networks based on disposal materials the cellular infrastructure are limited to places where there exists such a cellular network infrastructure. Snow Essay. The second approach is to form an ad-hoc network among all users wanting to communicate with each other. This means that all users participating in the ad-hoc network must be willing to forward data packets to and deductive research, make sure that the packets are delivered from source to destination. This form of networking is Snow Essay limited in in macbeth range by the individual nodes transmission ranges and White, is typically smaller compared to the range of cellular systems. This does not mean that the No Simple Solution Problem cellular approach is better than the Snow White Essay ad-hoc approach. New Product Pricing. Ad-hoc networks have several advantages compared to traditional cellular systems. These advantages include: N N N On demand setup Fault tolerance Unconstrained connectivity Ad-hoc networks do not rely on any pre-established infrastructure and can therefore be deployed in Snow White Essay places with no infrastructure. This is useful in disaster recovery situations and places with non-existing or damaged communication infrastructure where rapid deployment of a communication network is needed.
Adhoc networks can also be useful on conferences where people participating in the conference can form a temporary network without engaging the services of any pre-existing network. Because nodes are forwarding packets for each other, some sort of routing protocol is necessary to make the routing decisions. Currently there does not exist any standard for a routing protocol for ad-hoc networks, instead this is work in progress. Disposal Of Nuclear Materials A Serious Problem. Many problems remain to be solved before any standard can be determined. This thesis looks at some of these problems and Snow Essay, tries to inductive and deductive research, evaluate some of the currently proposed protocols. 1.2 Problem description The objective for White Essay this master thesis was to evaluate proposed routing protocols for wireless ad-hoc networks based on performance.
This evaluation should be done theoretically and through simulation. It was also desirable to compare the results with the results for routing protocols in a traditional wired network. At the beginning of this master thesis, no implementation of the protocols had been released, so the first main task was to strategies, implement some of the Snow White Essay protocols. The thesis also included the strategies goal to generate a simulation environment that could be used as a platform for further studies within the White Essay area of new product pricing ad-hoc networks. This simulation environment should if possible, be based on Network simulator 2 from Snow Berkeley. 9 The goal of this master thesis was to: N N N N N N Get a general understanding of african and native american ad-hoc networks. Snow Essay. Generate a simulation environment that could be used for further studies. Implement some of the proposed routing protocols for wireless ad-hoc networks.
Analyze the protocols theoretically and reflective essays, through simulation. Produce a classification of the protocols with respect to applicability in combinations of small/large networks, and mobile/semi-mobile nodes. Recommend protocols for specific network scenarios. 1.3 Related work Many routing protocols have been proposed , but few comparisons between the White different protocols have been made. Pricing Strategies. Of the work that has been done in this field, only the work done by Snow White the Monarch1 project at new product pricing, Carnegie Mellon University (CMU) has compared some of the different proposed routing protocols and evaluated them based on White Essay the same quantitative metrics. Inductive And Deductive. The result was presented in the article “A performance comparison of multi-hop ad hoc wireless network routing protocols”  that was released in the beginning of October 1998. There exist some other simulation results  that have been done on individual protocols. These simulations have however not used the same metrics and are therefore not comparable with each other. In parallel with our master thesis, a master thesis project in Gothenburg  implemented the AODV  protocol and tested it in a environment that consisted of 5 computers with wireless interfaces. White Essay. The cooperation between our projects and their project made it possible to personal reflective, share thoughts and ideas with each other. 1.4 Project organization The following persons have been involved in this master thesis project: Simulation study and master thesis authors M.Sc.
Tony Larsson M.Sc. Nicklas Hedman Supervisor at Ericsson Telecom AB, Switchlab Tekn.Lic. Per Johansson Examiner at Snow White, Lulea University of Technology Ph. D. Mikael Degermark Implementation study at Essay on Poverty: No Simple Solution to this Multi-faceted, Ericsson Mobile data design (ERV) in Snow Gothenburg M.Sc. Johan Kopman M.Sc.
Jerry Svedlund Supervisor at ERV M.Sc. Relations. Christoffer Kanljung Contribution of realistic scenarios Ph.D. student at Snow White Essay, Chalmers University of research Technology: Bartosz Mielczarek 1 MObile Networking ARCHitectures 10 1.5 Disposition This report consists of 8 chapters and two appendices. Chapters 1 and 2 explain the concept of ad-hoc networks and routing in general. Chapter 3 describes the different routing protocols, analyzes and compares them. Chapters 4 and 5 describe the simulator and the simulations that were made. White. Chapter 6 describes the implementation study of AODV that was made in pricing strategies Gothenburg.
Chapter 7 concludes the whole report and Snow Essay, chapter 8 is the references that we have used. The appendices contain some terminology, details about the implementation of AODV that we did for the simulator and some screenshots of the simulator. 1.6 Abbreviations AODV CBR CBRP DSDV DSR IEEE IETF LAN IP MAC MANET OLSR PDA QoS TCP TORA UDP WINET ZRP Ad-hoc On-demand Distance Vector Constant Bit Rate Cluster Based Routing Protocol Destination Sequenced Distance Vector Dynamic Source Routing Institute of Electrical and Electronics Engineers Internet Engineering Task Force Local Area Network Internet Protocol Media Access Protocol Mobile Ad-hoc NETworks Optimized Link State Routing Protocol Personal Digital Assistant Quality of Service Transmission Control Protocol Temporally Ordered Routing Algorithm User Datagram Protocol Wireless InterNET Zone Routing Protocol 11 2 General Concepts 2.1 Wireless ad-hoc networks 2.1.1 General A wireless ad-hoc network is a collection of mobile/semi-mobile nodes with no pre-established infrastructure, forming a temporary network. Each of the nodes has a wireless interface and Essay on Poverty: Solution Multi-faceted, communicate with each other over either radio or infrared. Laptop computers and personal digital assistants that communicate directly with each other are some examples of Snow White nodes in an ad-hoc network.
Nodes in the adhoc network are often mobile, but can also consist of stationary nodes, such as access points to the Internet. Semi mobile nodes can be used to deploy relay points in areas where relay points might be needed temporarily. And Native. Figure 1 shows a simple ad-hoc network with three nodes. The outermost nodes are not within transmitter range of each other. However the middle node can be used to forward packets between the outermost nodes.
The middle node is acting as a router and the three nodes have formed an ad-hoc network. Figure 1: Example of a simple ad-hoc network with three participating nodes. An ad-hoc network uses no centralized administration. This is to be sure that the network wont collapse just because one of the mobile nodes moves out of Snow White transmitter range of the of nuclear materials a serious problem others. Nodes should be able to White Essay, enter/leave the reflective essays network as they wish. Because of the Snow White Essay limited transmitter range of the nodes, multiple hops may be needed to essays, reach other nodes.
Every node wishing to participate in an ad-hoc network must be willing to forward packets for other nodes. Snow Essay. Thus every node acts both as a host and as a router. American. A node can be viewed as an abstract entity consisting of a router and a set of affiliated mobile hosts (Figure 2). A router is an entity, which, among other things runs a routing protocol. A mobile host is simply an IP-addressable host/entity in the traditional sense. Ad-hoc networks are also capable of handling topology changes and malfunctions in Snow White nodes. It is fixed through network reconfiguration. For instance, if a node leaves the network and causes link breakages, affected nodes can easily request new routes and the problem will be solved. This will slightly increase the delay, but the network will still be operational.
12 Wireless ad-hoc networks take advantage of the to this Multi-faceted Problem nature of the Essay wireless communication medium. In other words, in a wired network the physical cabling is done a priori restricting the connection topology of the nodes. This restriction is not present in the wireless domain and, provided that two nodes are within transmitter range of each other, an instantaneous link between them may form. Host Host Router Host Figure 2: Block diagram of Essay No Simple to this Multi-faceted Problem a mobile node acting both as hosts and White Essay, as router. 2.1.2 Usage There is no clear picture of what these kinds of networks will be used for.
The suggestions vary from document sharing at conferences to infrastructure enhancements and military applications. In areas where no infrastructure such as the Internet is available an why is disposal of nuclear materials a serious problem, ad-hoc network could be used by a group of wireless mobile hosts. This can be the case in areas where a network infrastructure may be undesirable due to reasons such as cost or convenience. Examples of Snow White Essay such situations include disaster recovery personnel or military troops in cases where the normal infrastructure is either unavailable or destroyed. Other examples include business associates wishing to share files in personal reflective essays an airport terminal, or a class of students needing to interact during a lecture. If each mobile host wishing to communicate is equipped with a wireless local area network interface, the group of mobile hosts may form an ad-hoc network.
Access to the Internet and access to resources in networks such as printers are features that probably also will be supported. 2.1.3 Characteristics Ad-hoc networks are often characterized by White Essay a dynamic topology due to the fact that nodes change their physical location by moving around. Reflective Essays. This favors routing protocols that dynamically discover routes over White Essay, conventional routing algorithms like distant vector and link state . Another characteristic is that a host/node have very limited CPU capacity, storage capacity, battery power and personal reflective, bandwidth, also referred to as a “thin client”. White Essay. This means that the power usage must be limited thus leading to a limited transmitter range. The access media, the radio environment, also has special characteristics that must be considered when designing protocols for ad-hoc networks. One example of why is disposal of nuclear problem this may be unidirectional links. These links arise when for example two nodes have different strength on their transmitters, allowing only one of the host to hear the White Essay other, but can also arise from disturbances from the personal essays surroundings.
Multihop in White Essay a radio environment may result in an overall transmit capacity gain and personal reflective, power gain, due to the squared relation between coverage and required output power. By using multihop, nodes can transmit the packets with a much lower output power. 13 2.2 Routing Because of the fact that it may be necessary to hop several hops (multi-hop) before a packet reaches the destination, a routing protocol is needed. Snow Essay. The routing protocol has two main functions, selection of routes for various source-destination pairs and the delivery of messages to their correct destination. The second function is personal conceptually straightforward using a variety of White Essay protocols and data structures (routing tables). This report is focused on and deductive research selecting and finding routes. 2.2.1 Conventional protocols If a routing protocol is needed, why not use a conventional routing protocol like link state or distance vector? They are well tested and most computer communications people are familiar with them. The main problem with link-state and distance vector is Snow White that they are designed for duncan in macbeth a static topology, which means that they would have problems to converge to a steady state in an ad-hoc network with a very frequently changing topology. Link state and distance vector would probably work very well in an ad-hoc network with low mobility, i.e. a network where the topology is not changing very often. The problem that still remains is that link-state and distance-vector are highly dependent on periodic control messages.
As the number of network nodes can be large, the potential number of destinations is White Essay also large. This requires large and frequent exchange of data among the duncan in macbeth network nodes. Snow White. This is in contradiction with the and deductive fact that all updates in Essay a wireless interconnected ad hoc network are transmitted over the air and thus are costly in resources such as bandwidth, battery power and CPU. Because both link-state and distance vector tries to maintain routes to all reachable destinations, it is necessary to maintain these routes and Essay Multi-faceted, this also wastes resources for the same reason as above. White. Another characteristic for conventional protocols are that they assume bi-directional links, e.g. that the new product pricing transmission between two hosts works equally well in both directions. In the wireless radio environment this is not always the Snow White case. Because many of the proposed ad-hoc routing protocols have a traditional routing protocol as underlying algorithm, it is necessary to understand the basic operation for and native conventional protocols like distance vector, link state and source routing. 2.2.2 Link State In link-state routing , each node maintains a view of the complete topology with a cost for each link. White. To keep these costs consistent; each node periodically broadcasts the link costs of its outgoing links to all other nodes using flooding. As each node receives this information, it updates its view of the network and applies a shortest path algorithm to inductive and deductive, choose the next-hop for each destination. Snow White. Some link costs in african american relations a node view can be incorrect because of long propagation delays, partitioned networks, etc.
Such inconsistent network topology views can lead to formation of routing-loops. These loops are however short-lived, because they disappear in the time it takes a message to traverse the diameter of the network. Snow Essay. 2.2.3 Distance Vector In distance vector  each node only monitors the cost of its outgoing links, but instead of research broadcasting this information to all nodes, it periodically broadcasts to each of its neighbors an Snow Essay, estimate of the shortest distance to inductive and deductive, every other node in the network. The receiving nodes then use this information to recalculate the routing tables, by using a shortest path algorithm. Compared to White Essay, link-state, distance vector is more computation efficient, easier to implement and requires much less storage space. However, it is well known that distance vector can cause the formation of both short-lived and long-lived routing loops. The primary cause for this is that the nodes choose their next-hops in a completely distributed manner based on information that can be stale. 2.2.4 Source Routing Source routing  means that each packet must carry the complete path that the packet should take through the waste of nuclear materials a serious network. The routing decision is therefore made at the source. The advantage with this approach is that it is very easy to White Essay, avoid routing loops.
The disadvantage is that each packet requires a slight overhead. 14 2.2.5 Flooding Many routing protocols uses broadcast to distribute control information, that is, send the and native control information from an White, origin node to all other nodes. New Product. A widely used form of broadcasting is Snow Essay flooding  and Essay No Simple Solution to this Multi-faceted Problem, operates as follows. The origin node sends its information to its neighbors (in the wireless case, this means all nodes that are within transmitter range). The neighbors relay it to their neighbors and so on, until the packet has reached all nodes in the network.
A node will only Snow, relay a packet once and to ensure this some sort of sequence number can be used. This sequence number is increased for each new packet a node sends. 2.2.6 Classification Routing protocols can be classified  into No Simple Problem different categories depending on their properties. N N N Centralized vs. Distributed Static vs.
Adaptive Reactive vs. Proactive One way to White, categorize the routing protocols is to duncan in macbeth, divide them into centralized and distributed algorithms. In centralized algorithms, all route choices are made at a central node, while in distributed algorithms, the computation of Essay routes is shared among the network nodes. Another classification of and deductive routing protocols relates to whether they change routes in White Essay response to personal reflective essays, the traffic input patterns. White Essay. In static algorithms, the route used by Solution source-destination pairs is White Essay fixed regardless of traffic conditions. It can only change in response to a node or link failure. This type of No Simple to this Multi-faceted Problem algorithm cannot achieve high throughput under a broad variety of traffic input patterns. Most major packet networks uses some form of adaptive routing where the routes used to White, route between source-destination pairs may change in response to congestion A third classification that is more related to ad-hoc networks is to classify the routing algorithms as either proactive or reactive. Proactive protocols attempt to continuously evaluate the routes within the network, so that when a packet needs to duncan, be forwarded, the Essay route is already known and can be immediately used. The family of Distance-Vector protocols is an example of a proactive scheme.
Reactive protocols, on the other hand, invoke a route determination procedure on demand only. Thus, when a route is new product pricing needed, some sort of global search procedure is employed. The family of classical flooding algorithms belongs to the reactive group. Proactive schemes have the advantage that when a route is needed, the delay before actual packets can be sent is very small. On the other side proactive schemes needs time to converge to a steady state. Essay. This can cause problems if the topology is waste of nuclear materials changing frequently. 15 3 Ad-hoc routing protocols This chapter describes the different ad-hoc routing protocols that we have chosen to simulate and analyze.
3.1 Desirable properties If the conventional routing protocols do not meet our demands, we need a new routing protocol. Essay. The question is what properties such protocols should have? These are some of the properties  that are desirable: Distributed operation The protocol should of course be distributed. It should not be dependent on a centralized controlling node. This is the case even for stationary networks. The difference is that nodes in an ad-hoc network can enter/leave the research network very easily and because of White Essay mobility the network can be partitioned. Loop free To improve the overall performance, we want the routing protocol to guarantee that the routes supplied are loop-free. This avoids any waste of bandwidth or CPU consumption. Demand based operation To minimize the control overhead in the network and thus not wasting network resources more than necessary, the why is waste disposal of nuclear a serious problem protocol should be reactive. This means that the protocol should only react when needed and Snow White Essay, that the protocol should not periodically broadcast control information. Unidirectional link support The radio environment can cause the formation of unidirectional links.
Utilization of these links and not only the bi-directional links improves the routing protocol performance. Security The radio environment is especially vulnerable to impersonation attacks, so to ensure the wanted behavior from the routing protocol, we need some sort of preventive security measures. And Native American Relations. Authentication and encryption is probably the way to go and the problem here lies within distributing keys among the Snow White nodes in the ad-hoc network. There are also discussions about using IP-sec  that uses tunneling to transport all packets. Power conservation The nodes in an ad-hoc network can be laptops and why is of nuclear materials, thin clients, such as PDAs that are very limited in battery power and therefore uses some sort of stand-by mode to save power.
It is therefore important that the routing protocol has support for these sleep-modes. Multiple routes To reduce the number of Essay reactions to topological changes and of nuclear materials, congestion multiple routes could be used. White Essay. If one route has become invalid, it is possible that another stored route could still be valid and african and native american, thus saving the routing protocol from initiating another route discovery procedure. Quality of service support Some sort of Quality of Service support is probably necessary to incorporate into the routing protocol. This has a lot to do with what these networks will be used for. It could for Snow instance be real-time traffic support. Inductive And Deductive. None of the proposed protocols from Snow White MANET have all these properties, but it is necessary to remember that the personal reflective protocols are still under development and are probably extended with more functionality. The primary function is still to find a route to the destination, not to Snow, find the best/optimal/shortest-path route. No Simple. The remainder of Snow Essay this chapter will describe the different routing protocols and analyze them theoretically.
16 3.2 MANET IETF has a working group named MANET (Mobile Ad-hoc Networks)  that is working in the field of adhoc networks. They are currently developing routing specifications for ad-hoc IP networks that support scaling to a couple of hundred nodes. Their goal is to be finished in the end of year 1999 and then introduce these specifications to the Internet standard tracks. Even if MANET currently is working on disposal materials problem routing protocols, it also serves as a meeting place and forum, so people can discuss issues concerning ad-hoc networks. Currently they have seven routing protocol drafts: N N N N N N N N AODV - Ad-hoc On Demand Distance Vector  ZRP - Zone Routing Protocol  TORA / IMEP - Temporally Ordered Routing Algorithm / Internet MANET Encapsulation Protocol  DSR - Dynamic Source Routing  CBRP - Cluster Based Routing Protocol  CEDAR - Core Extraction Distributed Ad hoc Routing  AMRoute – Ad-hoc Multicast Routing Protocol  OLSR - Optimized Link State Routing Protocol  Of these proposed protocols we have chosen to analyze AODV, DSR, ZRP, CBRP and TORA theoretically. Snow White. We have also analyzed DSDV, which is a proactive approach, as opposed to the other reactive protocols. We have not analyzed AMRoute because it is a multicast routing protocol, neither CEDAR because it is primary a QoS routing protocol, nor OLSR, because it was submitted as an essays, Internet draft so late. In those cases where a protocol supports both unicast and multicast routing we have only Snow White Essay, looked at reflective, the unicast routing part.
Of the theoretically analyzed protocols we have done simulations on AODV and DSR. 3.3 Destination Sequenced Distance Vector - DSDV 3.3.1 Description DSDV  is a hop-by-hop distance vector routing protocol that in each node has a routing table that for all reachable destinations stores the next-hop and number of hops for that destination. Essay. Like distance-vector, DSDV requires that each node periodically broadcast routing updates. The advantage with DSDV over traditional distance vector protocols is that DSDV guarantees loop-freedom. To guarantee loop-freedom DSDV uses a sequence numbers to on Poverty: Solution to this Multi-faceted, tag each route. The sequence number shows the Essay freshness of research a route and routes with higher sequence numbers are favorable. A route R is considered more favorable than R' if R has a greater sequence number or, if the routes have the same sequence number but R has lower hop-count. Snow White Essay. The sequence number is increased when a node A detects that a route to a destination D has broken. So the african and native american relations next time node A advertises its routes, it will advertise the route to Snow White, D with an infinite hop-count and a sequence number that is larger than before. DSDV basically is distance vector with small adjustments to make it better suited for ad-hoc networks.
These adjustments consist of triggered updates that will take care of topology changes in the time between broadcasts. To reduce the amount of information in new product pricing strategies these packets there are two types of update messages defined: full and White Essay, incremental dump. The full dump carries all available routing information and the incremental dump that only carries the information that has changed since the last dump. 3.3.2 Properties Because DSDV is dependent on periodic broadcasts it needs some time to converge before a route can be used. This converge time can probably be considered negligible in a static wired network, where the a serious topology is not changing so frequently. In an ad-hoc network on Snow the other hand, where the inductive and deductive research topology is Snow expected to be very dynamic, this converge time will probably mean a lot of dropped packets before a valid route is detected. The periodic broadcasts also add a large amount of overhead into african american the network. 17 3.4 Ad-hoc On Demand Distance vector - AODV 3.4.1 Description The Ad Hoc On-Demand Distance Vector (AODV)  routing protocol enables multi-hop routing between participating mobile nodes wishing to establish and Snow White, maintain an ad-hoc network. AODV is based upon the distance vector algorithm. The difference is that AODV is reactive, as opposed to proactive protocols like DV, i.e. AODV only african and native, requests a route when needed and Snow White Essay, does not require nodes to maintain routes to destinations that are not actively used in communications.
As long as the endpoints of a communication connection have valid routes to each other, AODV does not play any role. Features of this protocol include loop freedom and that link breakages cause immediate notifications to be sent to the affected set of nodes, but only that set. Additionally, AODV has support for multicast routing and personal, avoids the Bellman Ford counting to infinity problem . Snow White Essay. The use of reflective destination sequence numbers guarantees that a route is White Essay fresh. The algorithm uses different messages to discover and essays, maintain links. Whenever a node wants to Essay, try and find a route to another node, it broadcasts a Route Request (RREQ) to all its neighbors. The RREQ propagates through the network until it reaches the destination or a node with a fresh enough route to on Poverty: to this Multi-faceted, the destination. Snow Essay. Then the african american route is White made available by unicasting a RREP back to the source. The algorithm uses hello messages (a special RREP) that are broadcasted periodically to the immediate neighbors. These hello messages are local advertisements for the continued presence of the node and neighbors using routes through the broadcasting node will continue to mark the routes as valid. Essay To This Multi-faceted Problem. If hello messages stop coming from a particular node, the neighbor can assume that the node has moved away and mark that link to White, the node as broken and notify the duncan affected set of nodes by sending a link failure notification (a special RREP) to that set of nodes.
AODV also has a multicast route invalidation message, but because we do not cover multicast in this report we will not discuss this any further. Route table management AODV needs to Essay, keep track of the following information for duncan each route table entry: N N N N N N N Destination IP Address: IP address for the destination node. Destination Sequence Number: Sequence number for this destination. Hop Count: Number of Snow White hops to the destination. Next Hop: The neighbor, which has been designated to forward packets to the destination for this route entry. Lifetime: The time for which the route is personal essays considered valid. Essay. Active neighbor list: Neighbor nodes that are actively using this route entry. Request buffer: Makes sure that a request is only processed once. Route discovery A node broadcasts a RREQ when it needs a route to a destination and does not have one available. This can happen if the route to the destination is unknown, or if a previously valid route expires. After broadcasting a RREQ, the node waits for a RREP.
If the reply is not received within a certain time, the node may rebroadcast the RREQ or assume that there is no route to the destination. Forwarding of RREQs is done when the node receiving a RREQ does not have a route to new product strategies, the destination. It then rebroadcast the Snow RREQ. The node also creates a temporary reverse route to the Source IP Address in its routing table with next hop equal to new product, the IP address field of the neighboring node that sent the broadcast RREQ. This is done to keep track of a route back to the original node making the request, and might be used for an eventual RREP to find its way back to the requesting node. The route is temporary in the sense that it is valid for a much shorter time, than an actual route entry. When the RREQ reaches a node that either is the destination node or a node with a valid route to the destination, a RREP is generated and unicasted back to the requesting node.
While this RREP is Snow forwarded, a route is created to the destination and when the RREP reaches the source node, there exists a route from the source to the destination. 18 Route maintenance When a node detects that a route to a neighbor no longer is valid, it will remove the in macbeth routing entry and send a link failure message, a triggered route reply message to the neighbors that are actively using the route, informing them that this route no longer is valid. Snow Essay. For this purpose AODV uses a active neighbor list to keep track of the and deductive research neighbors that are using a particular route. The nodes that receive this message will repeat this procedure. Snow Essay. The message will eventually be received by the affected sources that can chose to either stop sending data or requesting a new route by sending out on Poverty: to this Multi-faceted Problem, a new RREQ. 3.4.2 Properties The advantage with AODV compared to classical routing protocols like distance vector and link-state is Snow White that AODV has greatly reduced the number of routing messages in the network. AODV achieves this by using a reactive approach. This is probably necessary in an ad-hoc network to get reasonably performance when the topology is changing often. AODV is also routing in the more traditional sense compared to on Poverty: Problem, for instance source routing based proposals like DSR (see 3.5). The advantage with a more traditional routing protocol in White an ad-hoc network is that connections from the ad-hoc network to a wired network like the Internet is most likely easier.
The sequence numbers that AODV uses represents the freshness of a route and is increased when something happens in the surrounding area. Why Is Waste Of Nuclear A Serious. The sequence prevents loops from being formed, but can however also be the Snow cause for new problems. What happens for instance when the sequence numbers no longer are synchronized in the network? This can happen when the network becomes partitioned, or the sequence numbers wrap around. AODV only and deductive research, support one route for each destination. It should however be fairly easy to Snow White Essay, modify AODV, so that it supports several routes per destination. On Poverty: No Simple To This Problem. Instead of requesting a new route when an old route becomes invalid, the next stored route to Snow Essay, that destination could be tried.
The probability for that route to waste disposal of nuclear problem, still be valid should be rather high. Although the Triggered Route Replies are reduced in number by only sending the Triggered Route Replies to affected senders, they need to traverse the whole way from the failure to Essay, the senders. This distance can be quite high in numbers of hops. AODV sends one Triggered RREP for every active neighbor in the active neighbor list for all entries that have been affected of a link failure. This can mean that each active neighbor can receive several triggered RREPs informing about the same link failure, but for different destinations, if a large fraction of the network traffic is routed through the same node and this node goes down. An aggregated solution would be more appropriate here.
AODV uses hello messages at the IP-level. This means that AODV does not need support from the Essay on Poverty: Solution to this Multi-faceted Problem link layer to work properly. It is however questionable if this kind of protocol can operate with good performance without support from the link layer. The hello messages adds a significant overhead to the protocol. Snow Essay. AODV does not support unidirectional links.
When a node receives a RREQ, it will setup a reverse route to the source by using the node that forwarded the RREQ as nexthop. This means that the route reply, in on Poverty: No Simple Solution to this most cases is unicasted back the Snow Essay same way as the route request used. Personal. Unidirectional link support would make it possible to utilize all links and not only the bi-directional links. It is however questionable if unidirectional links are desirable in a real environment. The acknowledgements in the MAC protocol IEEE 802.11 would for instance not work with unidirectional links. 19 3.5 Dynamic Source Routing - DSR 3.5.1 Description Dynamic Source Routing (DSR)  also belongs to Essay, the class of reactive protocols and allows nodes to dynamically discover a route across multiple network hops to pricing strategies, any destination. Source routing means that each packet in Snow White Essay its header carries the complete ordered list of nodes through which the in macbeth packet must pass. DSR uses no periodic routing messages (e.g. no router advertisements), thereby reducing network bandwidth overhead, conserving battery power and avoiding large routing updates throughout the ad-hoc network. Instead DSR relies on support from the MAC layer (the MAC layer should inform the White routing protocol about link failures). The two basic modes of operation in DSR are route discovery and No Simple Solution Multi-faceted Problem, route maintenance. Route discovery Route discovery is the mechanism whereby a node X wishing to Snow White, send a packet to personal, Y, obtains the source route to Y. Node X requests a route by broadcasting a Route Request (RREQ) packet.
Every node receiving this RREQ searches through its route cache for a route to Essay, the requested destination. DSR stores all known routes in its route cache. If no route is found, it forwards the in macbeth RREQ further and Snow White Essay, adds its own address to the recorded hop sequence. This request propagates through the network until either the destination or a node with a route to the destination is reached. When this happen a Route Reply (RREP) is unicasted back to the originator. This RREP packet contains the sequence of network hops through which it may reach the duncan target. In Route Discovery, a node first sends a RREQ with the Snow White Essay maximum propagation limit (hop limit) set to zero, prohibiting its neighbors from rebroadcasting it.
At the cost of a single broadcast packet, this mechanism allows a node to query the route caches of all its neighbors. Nodes can also operate their network interface in promiscuous mode, disabling the interface address filtering and causing the network protocol to in macbeth, receive all packets that the interface overhears. These packets are scanned for useful source routes or route error messages and then discarded. The route back to the originator can be retrieved in several ways. The simplest way is to reverse the hop record in the packet. Essay. However this assumes symmetrical links. To deal with this, DSR checks the route cache of the replying node. If a route is found, it is used instead.
Another way is to piggyback the reply on why is waste disposal materials a RREQ targeted at the originator. This means that DSR can compute correct routes in Snow the presence of essays asymmetric (unidirectional) links. Once a route is Snow White found, it is inductive and deductive stored in the cache with a time stamp and the route maintenance phase begins. Route maintenance Route maintenance is the mechanism by which a packet sender S detects if the network topology has changed so that it can no longer use its route to the destination D. Snow White Essay. This might happen because a host listed in a source route, move out of wireless transmission range or is turned off making the route unusable. A failed link is detected by either actively monitoring acknowledgements or passively by running in promiscuous mode, overhearing that a packet is Essay on Poverty: No Simple Solution Multi-faceted forwarded by a neighboring node. When route maintenance detects a problem with a route in use, a route error packet is sent back to the source node. When this error packet is received, the hop in error is removed from this hosts route cache, and all routes that contain this hop are truncated at this point.
3.5.2 Properties DSR uses the Essay key advantage of source routing. American Relations. Intermediate nodes do not need to maintain up-to-date routing information in order to route the packets they forward. There is also no need for periodic routing advertisement messages, which will lead to reduce network bandwidth overhead, particularly during periods when little or no significant host movement is taking place. Battery power is also conserved on the mobile hosts, both by not sending the advertisements and by Snow White not needing to receive them, a host could go down to sleep instead. Essay No Simple Solution Multi-faceted. This protocol has the advantage of learning routes by White scanning for information in packets that are received. A route from A to C through B means that A learns the route to C, but also that it will learn the route to B. Multi-faceted Problem. The source route will also mean that B learns the route to A and C and that C learns the Snow Essay route to duncan, A and B. Snow. This form of active learning is very good and reduces overhead in the network. 20 However, each packet carries a slight overhead containing the source route of the packet. This overhead grows when the packet has to african and native, go through more hops to Snow, reach the destination. So the packets sent will be slightly bigger, because of the overhead.
Running the interfaces in promiscuous mode is a serious security issue. Since the address filtering of the interface is turned off and duncan, all packets are scanned for information. A potential intruder could listen to all packets and Snow White, scan them for useful information such as passwords and credit card numbers. Applications have to provide the security by new product encrypting their data packets before transmission. The routing protocols are prime targets for impersonation attacks and must therefore also be encrypted. One way to achieve this is to use IPsec . DSR also has support for unidirectional links by the use of piggybacking the source route a new request. This can increase the White Essay performance in scenarios where we have a lot of unidirectional links.
We must however have a MAC protocol that also supports this. 3.6 Zone Routing Protocol - ZRP 3.6.1 Description Zone Routing Protocol (ZRP)  is a hybrid of a reactive and a proactive protocol. It divides the network into several routing zones and specifies two totally detached protocols that operate inside and between the routing zones. The Intrazone Routing Protocol (IARP) operates inside the routing zone and learns the minimum distance and routes to all the nodes within the zone. The protocol is not defined and can include any number of proactive protocols, such as Distance Vector or link-state routing. Different zones may operate with different intrazone protocols as long as the waste disposal of nuclear a serious protocols are restricted to those zones. Essay. A change in topology means that update information only propagates within the affected routing zones as opposed to affecting the entire network. The second protocol, the Interzone Routing Protocol (IERP) is reactive and is used for finding routes between different routing zones.
This is useful if the destination node does not lie within the routing zone. The protocol then broadcasts (i.e. bordercasts) a Route REQuest (RREQ) to all border nodes within the routing zone, which in turn forwards the request if the in macbeth destination node is not found within their routing zone. This procedure is Snow Essay repeated until the requested node is found and african american, a route reply is sent back to the source indicating the route. IERP uses a Bordercast Resolution Protocol (BRP)  that is included in ZRP. BRP provides bordercasting services, which do not exist in IP. Bordercasting is the process of sending IP datagrams from one node to all its peripheral nodes.
BRP keeps track of the peripheral nodes and resolves a border cast address to the individual IP-addresses of the peripheral nodes. The message that was bordercasted is White Essay then encapsulated into a BRP packet and sent to each peripheral node. Routing Zone A routing zone is and deductive defined as a set of nodes, within a specific minimum distance in number of Snow Essay hops from the duncan in macbeth node in question. The distance is referred to as the zone radius. In the example network (Figure 3), node S, A, F, B, C, G and H, all lie within a radius of two from node F. Even though node B also has a distance of 3 hops from node F, it is included in the zone since the shortest distance is only 2 hops. White. Border nodes or peripheral nodes are nodes whose minimum distance to the node in question is equal exactly to duncan, the zone radius. In Figure 3, nodes B and Essay, F are border nodes to new product strategies, S. White Essay. Consider the network in Figure 3. Node S wants to send a packet to research, node D. Since node D is not in the routing zone of Snow White S, a route request is sent to the border nodes B and F. Each border node checks to see if D is in their routing zone. Neither B nor F finds the requested node in their routing zone; thus the request is forwarded to the respectively border nodes. F sends the request to S, B, C and H while B sends the request to S, F, E and G. Duncan In Macbeth. Now the White requested node D is found within the personal essays routing zone of both C and Snow, E thus a reply is generated and sent back towards the source node S. 21 B E A Zone for D C S D F Zone for S G H Zone for F Figure 3: Network using ZRP. Essay Solution To This Problem. The dashed squares show the routing zones for nodes S and D. White. To prevent the requests from going back to previously queried routing zone, a Processed Request List is duncan used. This list stores previously processed requests and if a node receives a request that it already has processed, it is simply dropped.
3.6.2 Properties ZRP is Essay a very interesting protocol and can be adjusted of its operation to Multi-faceted Problem, the current network operational conditions (e.g. change the Snow Essay routing zone diameter). However this is duncan in macbeth not done dynamically, but instead it is Snow White suggested that this zone radius should be set by the administration of the network or with a default value by the manufacturer. The performance of american relations this protocol depends quite a lot on this decision. Snow White. Since this is a hybrid between proactive and reactive schemes, this protocol use advantages from both. Routes can be found very fast within the routing zone, while routes outside the inductive and deductive zone can be found by efficiently querying selected nodes in the network. Snow Essay. One problem is however that the proactive intrazone routing protocol is new product pricing not specified. The use of Snow White different intrazone routing protocols would mean that the nodes would have to support several different routing protocols. This is not a good idea when dealing with thin clients. It is better to pricing strategies, use the Snow Essay same intrazone routing protocol in the entire network. ZRP also limits propagation of information about topological changes to the neighborhood of the why is disposal of nuclear materials a serious change only (as opposed to a fully proactive scheme, which would basically flood the entire network when a change in topology occurred).
However, a change in Snow topology can affect several routing zones. 3.7 Temporally-Ordered Routing Algorithm - TORA 3.7.1 Description Temporally Ordered Routing Algorithm (TORA)  is duncan in macbeth a distributed routing protocol. The basic underlying algorithm is one in a family referred to Snow Essay, as link reversal algorithms. TORA is pricing designed to minimize reaction to Snow White, topological changes. Relations. A key concept in its design is that control messages are typically localized to a very small set of nodes. It guarantees that all routes are loop-free (temporary loops may form), and typically provides multiple routes for any source/destination pair.
It provides only the routing mechanism and depends on Internet MANET Encapsulation Protocol (IMEP ) for other underlying functions. TORA can be separated into three basic functions: creating routes, maintaining routes, and erasing routes. The creation of routes basically assigns directions to links in Snow White an undirected network or portion of the network, building a directed acyclic graph (DAG) rooted at the destination (See Figure 4). 22 D Figure 4: Directed acyclic graph rooted at destination. TORA associates a height with each node in the network. All messages in the network flow downstream, from a node with higher height to a node with lower height. A Serious Problem. Routes are discovered using Query (QRY) and Update (UPD) packets. When a node with no downstream links needs a route to a destination, it will broadcast a QRY packet. This QRY packet will propagate through the network until it reaches a node that has a route or the destination itself. Snow White Essay. Such a node will then broadcast a UPD packet that contains the node height. Every node receiving this UPD packet will set its own height to a larger height than specified in the UPD message.
The node will then broadcast its own UPD packet. This will result in a number of directed links from the pricing originator of the Snow White QRY packet to the destination. This process can result in multiple routes. Maintaining routes refers to reacting to in macbeth, topological changes in the network in Snow White a manner such that routes to the destination are re-established within a finite time, meaning that its directed portions return to a destination-oriented graph within a finite time. Upon detection of a network partition, all links in the portion of the network that has become partitioned from the destination are marked as undirected to personal essays, erase invalid routes. Snow White Essay. The erasing of routes is done using clear (CLR) messages.
3.7.2 Properties The protocols underlying link reversal algorithm will react to link changes through a simple localized single pass of the distributed algorithm. This prevents CLR packets to inductive and deductive research, propagate too far in White the network. A comparison made by new product pricing strategies the CMU Monarch project has however shown that the overhead in TORA is quite large because of the Essay use of IMEP. The graph is rooted at the destination, which has the lowest height. Duncan In Macbeth. However, the source originating the QRY does not necessarily have the highest height. This can lead to the situation, where multiple routes are possible from the source to Snow Essay, the destination, but only one route will be discovered. The reason for this is that the height is initially based on the distance in number of hops from the destination.
23 3.8 Internet MANET Encapsulation Protocol - IMEP 3.8.1 Description IMEP  is a protocol designed to support the operation of many routing protocols in Ad-hoc networks. The idea is to have a common general protocol that all routing protocols can make use of (see Figure 5). It incorporates many common mechanisms that the african american upper-layer protocol may need. These include: N N N N N Link status sensing Control message aggregation and encapsulation Broadcast reliability Network-layer address resolution Hooks for interrouter security authentication procedures IMEP also provides an architecture for MANET router identification, interface identification and addressing. Snow White Essay. IMEPs purpose is to improve overall performance by reducing the number of control messages and to put common functionality into one unified, generic protocol useful to all upper-level routing protocols. Routing IMEP IP Figure 5: IMEP in and deductive research the protocol stack. Of the currently purposed protocols, only Essay, TORA and reflective essays, OLSR use IMEP. It must however be noted that TORA and IMEP where designed by the same author. Snow Essay. 3.8.2 Properties The idea to inductive, have a general protocol for common basic features is White Essay good, but from a performance point of african relations view this is not such a good idea. It adds another layer to the protocol stack. As the work by the CMU Monarch projects has shown , IMEP generates a lot of overhead, mainly because of IMEPs neighbor discovery mechanism that generates at least one hello message per second, but also because of the reliable in-order delivery of the packets that IMEP provides.
3.9 Cluster Based Routing Protocol - CBRP 3.9.1 Description The idea behind CBRP  is to divide the nodes of an ad-hoc network into a number of Snow White Essay overlapping or disjoint clusters. One node is elected as cluster head for each cluster. This cluster head maintains the membership information for the cluster. Inter-cluster routes (routes within a cluster) are discovered dynamically using the membership information. 24 CBRP is based on source routing, similar to reflective, DSR. This means that intracluster routes (routes between clusters) are found by Snow White flooding the network with Route Requests (RREQ). The difference is that the cluster structure generally means that the number of nodes disturbed are much less. Flat routing protocols, i.e. only one level of hierarchy, might suffer from excessive overhead when scaled up. CBRP is like the other protocols fully distributed. This is necessary because of the very dynamic topology of the ad-hoc network. Furthermore, the african american relations protocol takes into consideration the existence of Snow unidirectional links.
Link sensing Each node in CBRP knows its bi-directional links to its neighbors as well as unidirectional links from its neighbors to itself. To handle this, each node must maintain a Neighbor Table (see Table 1). Table 1: Neighbor ID Neighbor 1 Neighbor 2 … Neighbor n Neighbor table. Link status Bi/unidirectional link to me Bi/unidirectional link to me … Bi/unidirectional link to me Role Is 1 a cluster head or member Is 2 a cluster head or member … Is n a cluster head or member Each node periodically broadcasts its neighbor table in pricing strategies a hello message. The hello message contains the node ID, the nodes role (cluster head, cluster member or undecided) and the neighbor table. The hello messages are used to update the neighbor tables at each node. White. If no hello message is why is waste disposal materials received from a certain node, that entry will be removed from the table. Clusters The cluster formation algorithm is very simple, the node with lowest node ID is elected as the cluster head. The nodes use the information in the hello messages to Snow White, decide whether or not they are the personal cluster heads. The cluster head regards all nodes it has bi-directinal links to as its member nodes.
A node regards itself as a member node to a particular cluster if it has a bi-directinal link to the cluster head. It is possible for a node to belong to several clusters. Cluster 1 Cluster 2 3 4 Cluster head Cluster head 1 2 6 Figure 6: 5 Bi-directional linked clusters. 25 Clusters are identified by White their respective cluster heads, which means that the cluster head must change as infrequently as possible. Why Is Disposal Materials A Serious. The algorithm is therefore not a strict lowest ID clustering algorithm. Snow Essay. A noncluster head never challenges the status of an existing cluster head. Only when two cluster-heads move next to each other, will one of why is waste disposal of nuclear materials them lose the White Essay role as cluster head. In Figure 6 node 1 is personal reflective cluster head for cluster 1 and node 2 is cluster head for cluster 2. Snow White. Routing Routing in CBRP is based on source routing and the route discovery is done, by why is of nuclear problem flooding the network with Route Requests (RREQ). White Essay. The clustering approach however means that fewer nodes are disturbed. This, because only the cluster heads are flooded.
If node X needs a route to node Y, node X will send out a RREQ, with a recorded source route listing only itself initially. Any node forwarding this packet will add its own ID in inductive and deductive this RREQ. Each node forwards a RREQ only once and it never forwards it to node that already appears in the recorded route. In CBRP, a RREQ will always follow a route with the following pattern: Source-Cluster head-Gateway-Cluster head-Gateway- . -Destination A gateway node for a cluster is White Essay a node that knows that it has a bi-directional or a unidirectional link to a node in another cluster. In Figure 6, node 6 is gateway node for cluster 1 and No Simple to this Multi-faceted Problem, node 4 is gateway node for cluster 2. The source unicasts the RREQ to its cluster head. Each cluster-head unicasts the RREQ to each of its bidirectionally linked neighbor clusters, which has not already appeared in the recorded route through the corresponding gateway. There does not necessarily have to Snow White Essay, be an why is waste disposal of nuclear materials, actual bi-directional link to a bi-directional linked neighbor cluster. For instance, in Figure 6 cluster 1 has a unidirectional link to cluster 2 through node 3 and cluster 2 has a unidirectional link to cluster 1 through node 5, and the clusters are therefore bidirectional linked neighbor clusters. This procedure continues until the target is found or another node can supply the route. When the RREQ reaches the target, the target may chose to memorize the reversed route to White Essay, the source. African American. It then copies the recorded route to Snow, a Route Reply packet and sends it back to the source.
3.9.2 Properties This protocol has a lot of common features with the earlier discussed protocols. It has a route discovery and route removal operation that has a lot in common with DSR and AODV. The clustering approach is probably a very good approach when dealing with large ad-hoc networks. The solution is more scalable than the other protocols, because it uses the clustering approach that limits the number of messages that need to be sent. CBRP also has the advantage that it utilizes unidirectional links.
One remaining question is and native american relations however how large each cluster should be. This parameter is critical to Snow, how the protocol will behave. 3.10 Comparison So far, the protocols have been analyzed theoretically. Table 2 summarizes and compares the african and native american result from these theoretical/qualitative analyses and shows what properties the protocols have and White Essay, do not have. Essay On Poverty: Solution To This Multi-faceted Problem. As it can be seen from Table 2, none of the protocols support power conservation or Quality of Service. This is however work in progress and will probably be added to the protocols. All protocols are distributed, thus none of the protocols is Essay dependent on a centralized node and inductive and deductive, can therefore easily reconfigure in White the event of inductive and deductive topology changes.
26 Table 2: Comparison between ad-hoc routing protocols. Snow White Essay. DSDV AODV DSR ZRP Loop-free Yes Yes Yes Yes Multiple routes Distributed Reactive Unidirectional link support QoS Support Multicast Security Power conservation Periodic broadcasts No Yes No No No No No No Yes No Yes Yes No No Yes No No Yes Yes Yes Yes Yes No No No No No No Yes Partially No No No No No Yes Requires reliable or sequenced data No No No No TORA/ IMEP No, short lived loops Yes Yes Yes No No No No No Yes (IMEP) Yes CBRP Yes Yes Yes Yes Yes No No No No Yes No DSDV is the only proactive protocol in this comparison. It is and deductive research also the protocol that have most in common with traditional routing protocol in wired networks. Essay. The sequence numbers were added to ensure loop-free routes. DSDV will probably be good enough in networks, which allows the protocol to inductive and deductive, converge in reasonable time. This however means that the mobility cannot be too high. The authors of DSDV came to the same conclusions and Snow White Essay, designed AODV, which is a reactive version of DSDV. They also added multicast capabilities, which will enhance the performance significantly when one node communicates with several nodes.
The reactive approach in AODV has many similarities with the on Poverty: Solution to this reactive approach of White Essay DSR. They both have a route discovery mode that uses request messages to find new routes. The difference is that DSR is based on in macbeth source routing and will learn more routes than AODV. White. DSR also has the why is waste of nuclear a serious advantage that it supports unidirectional links. DSR has however one major drawback and it is the Snow Essay source route that must be carried in each packet. This can be quite costly, especially when QoS is going to be used. ZRP and CBRP are two very interesting proposals that divide the personal reflective essays network into several zones/clusters. This approach is probably a very good solution for large networks. Within the zones/clusters they have a more proactive scheme and between the zones/clusters they have a reactive scheme that have many similarities with the operation of AODV and White Essay, DSR. They have for instance a route discovery phase that sends request through the network. Pricing. The difference between ZRP and Snow White Essay, CBRP is how the network is divided.
In ZRP all zones are overlapping and in CBRP clusters can be both overlapping and disjoint. And Deductive. None of the presented protocols are adaptive, meaning that the Essay protocols do not take any smart routing decisions when the traffic load in the network is in macbeth taken into consideration. As a route selection criteria the proposed protocols use metrics such as shortest number of hops and quickest response time to a request. This can lead to the situation where all packets are routed through the same node even if there exist better routes where the traffic load is not as large. 27 4 Simulation Environment The simulator we have used to simulate the ad-hoc routing protocols in is the Network Simulator 2 (ns)  from Berkeley. To simulate the mobile wireless radio environment we have used a mobility extension to ns that is developed by the CMU Monarch project at Carnegie Mellon University. 4.1 Network Simulator Network simulator 2 is the result of an on-going effort of research and development that is administrated by researchers at Berkeley. White Essay. It is a discrete event simulator targeted at networking research. It provides substantial support for simulation of waste a serious TCP, routing, and multicast protocols. The simulator is Essay written in C++ and a script language called OTcl2.
Ns uses an Otcl interpreter towards the user. Why Is Disposal Of Nuclear A Serious Problem. This means that the user writes an OTcl script that defines the network (number of nodes, links), the traffic in the network (sources, destinations, type of traffic) and which protocols it will use. This script is then used by ns during the simulations. The result of the simulations is an output trace file that can be used to White, do data processing (calculate delay, throughput etc) and to visualize the reflective essays simulation with a program called Network Animator (NAM). See Appendix C for Snow White Essay a screenshot of NAM. NAM is a very good visualization tool that visualizes the american packets as they propagate through the network. An overview of Snow White how a simulation is done in ns is american shown in White Figure 7. Otcl script Network Simulator 2 Output Data processing Network Animator Figure 7: Network simulator 2. Personal Reflective Essays. The current version3 of the Network simulator does not support mobile wireless environments. The Network simulator alone is Snow White only intended for stationary networks with wired links. This caused us some problems in the beginning of this master thesis.
We needed mobility and therefore started to design and implement a mobility model that would extend the simulator. We also started to implement the AODV protocol. This implementation of AODV is materials a serious problem compatible with NAM and therefore gives a good picture of how AODV behaves. It is very easy to follow for Snow White instance the route discovery procedure. On Poverty: To This Multi-faceted. About two months later, in Essay August 1998, two separate mobility extensions were released. These extensions had everything that we wanted from an waste disposal, extension, so we decided to use one of them. This however meant that the implementation of Essay AODV that we made earlier no longer was compatible and had to be ported. 2 3 Object Tool Command Language Network simulator 2.1b3 28 4.2 Mobility extension There currently exist two mobility extensions to essays, ns.
These are: N N Wireless mobility extension developed by the CMU Monarch projects . Essay. Mobility support, mobile IP and wireless channel support developed by C. Perkins at african and native, Sun Microsystems . The ns group at Berkeley has as intention to integrate both these extensions to ns. This work is however not complete yet. We have chosen to use the CMU Monarch extension, because this extension is targeted at ad-hoc networks. The version of the extension that we have worked with4 adds the following features5 to the Network simulator.
Node mobility Each mobile node is an independent entity that is responsible for computing its own position and velocity as a function of time. Nodes move around according to a movement pattern specified at the beginning of the simulation. Realistic physical layers Propagation models are used to decide how far packets can travel in air. These models also consider propagation delays, capture effects and carrier sense . MAC 802.11 An implementation of the IEEE 802.11 Media Access Protocol (MAC)  protocol was included in the extension. The MAC layer handles collision detection, fragmentation and acknowledgements. This protocol may also be used to White Essay, detect transmission errors. Personal. 802.11 is a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) protocol. It avoids collisions by checking the channel before using it. If the channel is free, it can start sending, if not, it must wait a random amount of White Essay time before checking again. For each retry an exponential backoff algorithm will be used.
In a wireless environment it cannot be assumed that all stations hear each other. If a station senses the medium, as free, it does not necessarily mean that the medium is new product strategies free around the receiver area. This problem is known as the hidden terminal problem and to overcome these problems the Snow White Collision Avoidance mechanism together with a positive acknowledgement scheme is used. The positive acknowledgement scheme means that the receiver sends an inductive, acknowledgement when it receives a packet. The sender will try to retransmit this packet until it receives the acknowledgement or the number of retransmits exceeds the maximum number of retransmits. 802.11 also support power saving and security. Power saving allows packets to be buffered even if the system is White asleep. Security is pricing provided by an algorithm called Wired Equivalent Privacy (WEP). It supports authentication and encryption. WEP is White a Pseudo Random Number Generator (PRNG) and strategies, is based on White RSAs RC4. Why Is Problem. One of the most important features of Snow 802.11 is the why is waste disposal ad-hoc mode, which allows users to build up Wireless LANs without an infrastructure (without an access point).
Address Resolution Protocol The Address Resolution Protocol, ARP  is implemented. ARP translates IP-addresses to hardware MAC addresses. This takes place before the packets are sent down to the MAC layer. Ad-hockey Ad-hockey is an application that makes it possible to visualize the mobile nodes as they move around and send/receives packets. Ad-hockey can also be used as a scenario generator tool to create the input files necessary for Snow the simulations. This is done, by positioning nodes in a specified area.
Each node is then given a movement pattern consisting of movement directions at different waypoints, speed, pause times and communication patterns. Screenshots of ad-hockey can be seen in Appendix C. 4 Version 1.0.0-beta, released in the middle of August. At the end of on Poverty: Solution Problem November 1998, the CMU Monarch projects released version 1.1.0 of the extension. This new version contains some bug fixes and implementations of the Snow AODV and TORA protocols. 5 29 Radio network interfaces This is a model of the hardware that actually transmits the packet onto inductive research the channel with a certain power and modulation scheme .
Transmission power The radius of the transmitter with an White Essay, omni-directional antenna is about 250 meters in this extension. Antenna gain and receiver sensitivity Different antennas are available for simulations. Ad-hoc routing protocols Both DSR and DSDV have been implemented and added to this extension. 4.2.1 Shared media The extension is and native relations based on a shared media model (Ethernet in the air). This means that all mobile nodes have one or more network interfaces that are connected to a channel (see Figure 8). Essay. A channel represents a particular radio frequency with a particular modulation and coding scheme. Channels are orthogonal, meaning that packets sent on one channel do not interfere with the transmission and reception of and deductive packets on another channel. The basic operation is as follows, every packet that is sent / put on the channel is received / copied to all mobile nodes connected to the same channel.
When a mobile nodes receive a packet, it first determines if it possible for it to receive the packet. This is determined by the radio propagation model, based on the transmitter range, the distance that the packet has traveled and the amount of bit errors. Mobile Node Mobile Node Mobile Node Channel Figure 8: Shared media model. 4.2.2 Mobile node Each mobile node (Figure 9) makes use of a routing agent for the purpose of calculating routes to other nodes in the ad-hoc network. Packets are sent from the application and are received by the routing agent. The agent decides a path that the packet must travel in order to White, reach its destination and stamps it with this information. Relations. It then sends the packet down to the link layer. The link layer level uses an Address Resolution Protocol (ARP) to decide the hardware addresses of neighboring nodes and map IP addresses to their correct interfaces. When this information is known, the packet is sent down to the interface queue and awaits a signal from the Snow Multiple Access Control (MAC) protocol.
When the MAC layer decides it is ok to send it onto the channel, it fetches the packet from the queue and new product strategies, hands it over to the network interface which in turn sends the packet onto the radio channel. This packet is copied and is delivered to all network interfaces at the time at which the first bit of the packet would begin arriving at Snow White, the interface in a physical system. Each network interface stamps the packet with the receiving interfaces properties and then invokes the propagation model. Inductive And Deductive. The propagation model uses the transmit and receive stamps to determine the power with which the interface will receive the Snow Essay packet. The receiving network interfaces then use their properties to determine if they actually successfully received the packet, and sends it to the MAC layer if appropriate. If the MAC layer receives the packet error- and of nuclear a serious, collision- free, it passes the packet to Snow White Essay, the mobiles entry point. From there it reaches a demultiplexer, which decides if the packet should be forwarded again, or if it has reached its destination node. If the destination node is reached, the packet is sent to a port demultiplexer, which decides to what application the in macbeth packet should be delivered. If the packet should be forwarded again the routing agent will be called and the procedure will be repeated. 30 Entry point M U X Application Routing Agent Link Layer ARP Queue MAC Propagation model Network Interface Channel Figure 9: A mobile node.
4.3 Simulation overview A typical simulation with ns and the mobility extension is shown in Figure 10. Basically it consists of generating the following input files to ns: N N A scenario file that describes the movement pattern of the nodes. A communication file that describes the traffic in the network. Essay. These files can be generated by drawing them by hand using the visualization tool Ad-hockey (see 4.2) or by generating completely randomized movement and communication patterns with a script. These files are then used for the simulation and as a result from this, a trace file is generated as output. Prior to the simulation, the parameters that are going to be traced during the simulation must be selected. The trace file can then be scanned and analyzed for the various parameters that we want to measure.
This can be used as data for american plots with for instance Gnuplot. The trace file can also be used to visualize the simulation run with either Ad-hockey or Network animator. 31 Scenario generation Scenario file Communication file Mobility extension Network Simulator 2 Output files Data processing Ad-hockey GnuPlot Figure 10: Network animator Simulation overview. 4.4 Modifications To be able to Snow White Essay, use ns for the simulations, we had to do some modifications. First of all, we did not have the routing protocols we wanted to simulate, so one of the first steps was to implement the protocols. 4.4.1 AODV We have implemented the AODV protocol (for more details, see appendix B). The implementation is why is disposal problem done according to the AODV draft  released in White Essay August 1998. It must however be noted that a new version of the draft  was released in the end of November 1998. And Deductive. The new draft contains some changes that would enhance the performance. These changes that affect the unicast routing part is primarily: N N Reduced or complete elimination of hello messages. White. Updates to important parameters to reflect recent simulation experiences.
To be able to test how the hello messages and link layer support affects the behavior of the protocol we have implemented three versions: N N N AODV with only on Poverty: No Simple Problem, IP-based hello messages AODV with only Link Layer notification of broken links AODV with both IP-based hello messages and Link layer notification of broken links The implementation of the White different versions has some major differences that will affect the performance. First of all AODV with only research, MAC-layer support will not get the routes to the neighbors installed in the routing table, neither will it update the routes to Snow White Essay, the neighbor who forwarded a message to you. Both AODV versions that have hello messages will have this neighbor detection process that keeps track of the neighbors. This means that the protocols with this feature will have more information in the 32 routing tables. Without this support, buffering of the packets may be necessary while a request is sent out in search for a node that could be a neighbor. It must however be noted that the removal of relations hello messages somewhat changes the behavior of the AODV protocol. Snow Essay. The hello messages add overhead to new product strategies, the protocol, but also gives us some prior knowledge of link breakages. Removing the hello messages makes the protocol completely on-demand, broken links can only Snow White, be detected when actually sending something on the broken link. The DSR implementation that was included in the mobility extension used a sendbuffer that buffered all packets that the application sent while the routing protocol searched for a route. To get a fair comparison of the protocols we implemented the same feature for new product AODV. This buffer can hold 64 packets and packets are allowed to stay in the buffer for White 8 seconds.
The parameters that can be adjusted for AODV and and deductive research, the values we have used is shown in Table 3. Some of White Essay these parameters are very important and affects the performance of the protocol in drastic ways. The hello interval is maybe the most important parameter when dealing with AODV that uses hello messages. If the interval is too long, link breakages would not be detected fast enough, but if the interval is to short, a great amount of extra control overhead would be added. Most of the parameters in Table 3 are obvious. The maximum rate for sending replies prevents a node to do a triggered route reply storm.
This means that AODV in each node is only allowed to send one triggered RREP per personal second for each broken route. This could for instance happen if a forwarding node receives a lot of data packets that the node no longer has a route for. In this case the node should only send a triggered RREP, as a response to the first data packet and Essay, if the waste disposal of nuclear materials a serious problem node keeps receiving data packets after that, a triggered RREP is only allowed to be sent once per Snow Essay second. Table 3: Constants used in the AODV implementation. Parameter Hello interval Active route timeout Route reply lifetime Allowed hello loss Request retries Time between retransmitted requests Time to hold packets awaiting routes Maximum rate for sending replies for a route Value 1,5 s 300 s 300 s 2 3 3s 8s 1/s 4.4.2 DSR The DSR implementation that came with the and deductive extension uses promiscuous mode (i.e. Snow White Essay. eavesdropping), which means that the protocol learns information from american relations packets that it overhears. The question is how realistic this is in a real environment. White. In a real case scenario we will probably have some sort of encryption, probably IP-Sec that uses IP-Sec tunneling to transport messages. We have made some small change to DSR that makes it possible to turn the eavesdropping feature on in macbeth and off. The parameters that are configurable for White DSR are shown in Table 4. These values are the values specified in the DSR draft and have not been changed. The nonpropagating timeout is the time a node waits for a reply for a nonpropagating search. A nonpropagating search is a request that first goes to the neighbors.
If the neighbors do not answer in this specified amount of a time, a new request that will be forwarded by the neighbors will be sent. The sendbuffer in the DSR can hold 64 packets and the packets are allowed to pricing strategies, stay in the buffer for 30 seconds Table 4: Constants used in the DSR implementation. Essay. Parameter Time between retransmitted requests Size of source route header carrying n addresses Timeout for duncan nonpropagating search Time to hold packets awaiting routes Maximum rate for sending replies for a route 33 Value 500 ms 4n + 4 bytes 30 ms 30 s 1/s 4.4.3 DSDV The extension also included an implementation of the DSDV protocol. Snow White Essay. This implementation is actually two implementations that handle the triggered update a little different. In the first version only Essay to this Multi-faceted Problem, a new metric for a destination causes a triggered update to be sent. In the Snow Essay second version, a new sequence number for a destination causes a triggered update to be sent. We have modified DSDV so it always uses the version that triggers on new sequence numbers. This is the waste disposal of nuclear materials version that, we feel behaves according to Snow White, the specification of DSDV. The parameters for in macbeth DSDV are shown in Table 5 and are as specified in the DSDV paper .
Table 5: Constants used in the DSDV implementation. Parameter Periodic route update interval Periodic updates missed before link declared broken Route advertisement aggregation time Maximum packets buffered per node per destination Value 15 s 3 1s 5 4.4.4 Flooding We have implemented a simple flooding protocol that simply floods all user data packets to all nodes in the network. To have some sort cleverness in this flooding and avoiding data to bounce back and forth we use a sequence number in each packet. This sequence number is incremented for each new packet. Each node keeps track of Snow White (source IP, sequence number) for all destinations and does not process a packet if the packet has a sequence number smaller than the stored sequence number. The idea was to do the simulations on the flooding protocol and compare the results with the results for the routing protocols. After some initial simulations on flooding this plan was abandoned. The simulations took too long to duncan in macbeth, complete.
The reason is that flooding generates too many packets (events in the simulator). 4.4.5 The simulator To the actual simulator (ns + extension) we have added some new features to allow us to Snow, make the wanted measurements. Obstacles The visualization/scenario generator tool, Ad-hockey, allows the user to place obstacles (lines and boxes) into the scenario. The problem is that ns do not use these obstacles for any kind of computation. Two nodes can communicate, even through a wall. We wanted to simulate the protocols in a few realistic scenarios, so we added these computations to ns. The calculations consisted of two parts. The first part was to strategies, store all obstacles in a database that we later could use when calculating the intersection points and the second part was to extend the propagation model with the actual computations. The computations merely consisted of deciding if there existed an Snow White, intersection point between the straight line from the sending node to the receiving node and any obstacle in the database.
If such an intersection point exists, the why is of nuclear materials problem communication is simply cut of. White. No fading of the inductive and deductive research signal, reflections etc is taken into consideration. The model is Snow Essay therefore very simple. The problem with these computations is that it adds a lot of overhead in the simulations. The simulations will take significantly longer time to on Poverty: Solution to this, complete. Snow White Essay. The extra computation must be done for all packets. In a large scenario with many nodes that are sending a lot of inductive research traffic this will increase the simulation time significantly. Version management To allow us to test different versions of one protocol simultaneous, we have added a version control to ns. This means that it is possible to give a version number to a protocol when the Essay simulation starts. This version number is given to the specified protocol and and deductive research, it is then up to the programmer to use it.
We currently use this feature with both AODV and DSR. The different versions are: N N N N N AODV 1 = AODV with only hello messages. AODV 2 = AODV with only MAC-layer feedback. AODV 3 = AODV with both hello messages and MAC-layer feedback. DSR 1 = DSR with eavesdropping. DSR 2 = DSR without eavesdropping. White Essay. 34 5 Simulation study The protocols that we have simulated are DSDV, AODV and DSR. DSDV is only used to get a comparison of how much better/worse the MANET protocols are than an ordinary proactive protocol. The simulations were conducted on an Intel PC with a Pentium-2 processor at 400 MHz, 128 Mbytes of duncan in macbeth RAM running FreeBSD6. 5.1 Measurements Before we go into the actual simulations, we will discuss which parameters  that are interesting to measure when studying routing protocols in an ad-hoc network.
There are two main performance measures that are substantially affected by the routing algorithm, the average end-to-end throughput (quantity of service) and the average end-to-end delay (quality of service). White Essay. 5.1.1 Quantitative metrics The measurements that we have conducted can be seen from two angels: externally and internally. The external view is what the pricing strategies application/user sees and the internal view is how the routing protocol behaves. The external measurements are basically the end-to-end throughput and delay. The internal behavior can further be divided into routing accuracy and routing efficiency. Snow White. N N Routing Efficiency: How much of the sent data is actually delivered to the destination? How much routing overhead is required to find routes? Routing Accuracy: How accurate, measured in number of hops are the supplied routes compared to the optimal shortest path.
5.1.2 Parameters The metrics has to be measured against some parameter that describes the characteristic behavior of an adhoc network and waste materials a serious problem, can be varied in a controlled way. The parameters that we have chosen to simulate with are: N N N Mobility, which probably is one of the most important characteristics of an Essay, ad-hoc network. This will affect the dynamic topology, links will go up and down. Offered network load. The load that we actually offer the new product strategies network. This can be characterized by three parameters: packet size, number of Snow White connections and duncan, the rate that we are sending the packets with. Network size (number of Snow White nodes, the on Poverty: to this Multi-faceted size of the area that the White Essay nodes are moving within). The network size basically determines the Essay to this Multi-faceted Problem connectivity. Fewer nodes in the same area mean fewer neighbors to send requests to, but also smaller probability for collisions.
5.1.3 Mobility Because mobility is an important metric when evaluating ad-hoc networks we need some definition of mobility. There exist many definitions of mobility. The CMU Monarch project  has for instance used the pause time in the waypoints as a definition of mobility. If a node has a low pause time, it will almost constantly be moving, which would mean a high mobility. White Essay. If a node has a large pause time it will stand still most of the time and have a low mobility. We did not think that this mobility definition was good enough, because even if the new product pricing pause time is low and all nodes are constantly moving, they could all be moving with a very slow speed in the same area. We have defined mobility a little differently. Our definition is based on the relative movement of the nodes. This definition gives a very good picture of how the nodes are moving relatively to each other. The definition is as follows: 6 FreeBSD 2.2.6 35 If several nodes move for Snow a certain time, then the mobility is the average change in duncan distance between all nodes over that period of time.
This time is the simulation time T. Mobility is a function of both the speed and the movement pattern. It is calculated with a certain sampling rate. Snow White Essay. During the simulations, we have used 0.1 seconds as sampling rate. This is the inductive and deductive default time when logging the movement in Snow Essay the simulations, so it was appropriate to duncan, use the same value when calculating the Essay mobility. Table 6 shows all variables that are used in the equations for the mobility factor. Table 6: Variable name dist(nx, ny)t n i Ax(t) Mx T t Mob Mobility variables.
Description the new product pricing distance between node x and node y at time t number of White nodes Index Average distance for node x to all other nodes at time t Average mobility for node x relative to all other nodes during the entire simulation time Simulation time Granularity, simulation step Mobility for in macbeth entire scenario First of all, the average distance from each node to all other nodes has to be calculated. This has to be done at times t = 0, t = 0+X, t = 0+2X, . t = simulation time. For the White node x at time t the duncan in macbeth formula is: n ¦ dist (n , n ) x Ax(t) = i i1 (5.1) n 1 After that, with the use of (5.1), the average mobility for that particular node has to be calculated. This is the average change in distance during a whole simulation. The mobility for node x is: T t ¦ A (t ) A (t 't ) x Mx = x t0 (5.2) T 't Finally, the mobility for the whole scenario is the sum of the Essay mobility for all nodes (5.2) divided with the number of nodes: n ¦M Mob = i i1 (5.3) n The unit for the mobility factor (5.3) is m/s.
The mobility factor therefore gives a picture of the average speed of the distance change between the nodes. Figure 11 shows some basic examples of how this mobility factor will reflect the actual movement. If the nodes are standing still, this will of course lead to a mobility of 0, but this would also be the case when the nodes relative movement is zero, for american example when the nodes are moving in parallel with the same speed. It is only when the Snow White nodes have a movement relative to each other that the mobility factor will be greater than zero. 36 Our mobility definition reflects how the mobility affects the dynamic topology, without considering obstacles or surroundings. Standing still 0.0 Parallel movement 0.0 Figure 11: Relative movement 0.0 Example of new product strategies mobility. The reason for choosing mobility as a parameter in the simulations is first of all that the Snow Essay mobility is one of the most important characteristics of an ad-hoc network. But also because mobility is a parameter that is easy to grasp for people in african american general. Snow White. Everyone has a rather good picture of what it means if the mobility is increased.
We have tested the mobility factor to see how it affects the dynamic topology. As it can be seen in Figure 12, the number of and native relations link changes is Snow Essay directly proportional to the mobility factor. Duncan In Macbeth. A link change basically means that a link changes state from Snow either up/down to down/up. The plot is the average values for all simulations that we have done using 50 nodes and an environment size of 1000x1000 meters. 3500 3000 Avg nr of link changes 2500 2000 1500 1000 500 0 0 0.5 Figure 12: 1 1.5 2 Mobility 2.5 3 3.5 Relation between the strategies number of link changes and mobility. 37 4 5.2 Simulation setup In this chapter we will describe how the Snow White simulations were done. We have done 4 different types of simulations: N N N N Mobility simulations: We vary the mobility to see how it affects the different metrics that we are measuring. Offered load simulations: We vary the load that we offer the network, to strategies, see how the protocols behave when for White instance the duncan in macbeth load is high. Snow White. Network size simulations: We vary the number of nodes in and native american the network. Realistic simulations: A few realistic scenarios were designed.
These simulations do not give a general view of the protocol, but instead tests certain characteristics of the Snow White protocols. Materials A Serious Problem. Because we had different versions of both AODV and DSR we decided to first compare the different versions of the same protocol. After that we did a more general comparison where we used one version of each protocol and Snow, compared them against DSDV. Reflective Essays. The comparisons made are therefore: N N N Comparison of AODV with only hello messages, AODV with only link layer support and ADOV with both hello messages and Snow, link layer support. Comparison of DSR with and without eavesdropping. Reflective Essays. Comparison of DSDV, AODV with both hello messages and Snow White Essay, link layer support and DSR without eavesdropping. The reason for choosing DSR without eavesdropping in the last comparison, is as mentioned earlier that this is more realistic. Security features like encryption will prohibit eavesdropping in the future. The choice of AODV with both link layer support and hello messages was made because first of all, link layer support is probably a necessity to achieve a performance that is strategies good enough and secondly because the removal of Snow hello messages somewhat changes the overall functionality of AODV. Removal of reflective essays hello messages would of course save us from the overhead of the hello messages, but also makes the protocol completely on-demand. A broken link could only be detected when a packet needs to be sent on the link.
In all simulations, except the White Essay realistic scenario simulations, we have used a randomized scenario. The randomized scenarios have different parameters that affect the movement patterns. The parameters that can be changed are: N N N N N Maximum speed: Every time a speed is going to on Poverty: Problem, be randomized it is randomized in Essay the interval [0,maximum speed]. Number of nodes: This was constant during the simulations. We used 50 nodes for all simulation except the size simulation where we varied the and deductive research number of nodes.
Environment size: Determines the size of the environment. We have used a size of White 1000 x 1000 meters for all simulations except the inductive research realistic simulations where we have used 1500 x 900. Simulation time: The time for Snow Essay which the simulations will be run at. We have used a simulation time of 250 seconds for all simulations except the realistic simulations where we used 900 seconds. Pause time: Pause time is the in macbeth time for which a node stands still before randomizing a new destination and the speed that will be used to Snow, reach this destination.
We have used a pause time for 1 second in all simulations. The randomizing of scenarios works like this: first of all every node stands still for Essay to this Problem pause time seconds. White Essay. After that each node selects a random destination, a waypoint somewhere in reflective the environment space. Each node also randomizes a speed that will be used when moving to the waypoint. This speed is randomized uniformly in the interval 0 to maximum speed. Every time a node reaches a waypoint, this procedure will be repeated. A factor that we have not taken into consideration with the Snow Essay scenarios is the disposal a serious problem fact that a real person is not likely to stand on the same place if the connection goes down. Essay. A real person is waste disposal of nuclear materials more likely to find a place where the reception is good enough. The system would be to complex if this factor were included also. Essay. We have assumed bi-directional links during all our simulations, i.e. the links work equally well in personal reflective both directions.
It is questionable if unidirectional links are desirable when using the IEEE 802.11 MAC protocol, because bi-directional links are necessary if 802.11 acknowledgements are supposed to be used. Snow Essay. 38 5.3 Mobility simulations 5.3.1 Setup The simulations where we varied the mobility where done by randomizing scenario files. This method is on Poverty: Solution Problem very hard to perform, because we cannot prior a scenario generation say that we want a mobility factor of White exactly X. Instead we used the maximum speed parameter to control the scenario. The simulation parameters that have been used for the mobility simulations are shown in Table 7. Table 7: Parameters used during mobility simulations. Inductive And Deductive. Parameter Transmitter range Bandwidth Simulation time Number of White Essay nodes Pause time Environment size Traffic type Packet rate Packet size Number of flows Value 250 m 2 Mbit 250 s 50 1s 1000x1000 m Constant Bit Rate 5 packets/s 64 byte 15 The scenario is a very crucial part of the simulation. We have therefore collected 10 measurements for each wanted mobility factor. The mobility factors that we simulated on are: 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5.
Because of the hard part of getting scenarios that are precise we have used an interval of r0.1 for disposal of nuclear materials a serious problem the above mentioned mobility factors. The scenarios that where created where then analyzed in terms of unreachable hosts. We did not want to investigate network partition at this stage, so all scenarios with extremely high degree of unreachable hosts where discarded. By increasing the Snow maximum speed in the scenario generation, the mobility will also increase. A mobility factor of 3.5 approximately corresponds to a maximum speed of 20 m/s. For the randomized simulations we have varied the and deductive maximum speed in the interval 0 to 20 m/s. Snow. A speed of 20 m/s corresponds the speed of a vehicle, which will lead to a high mobility. We used the african and native american same communication pattern for all mobility simulations. The traffic pattern consisted of 15 CBR sources that started at different times. Essay. We did not use TCP for the simulations, because we did not want to investigate TCP, which uses flow control, retransmit features and so on. We wanted to get a general view of how the routing protocol behaves.
The communication pattern was randomly created. Waste Disposal Of Nuclear A Serious Problem. The parameters that was specified when randomizing the communication pattern were the Snow White Essay number of wanted sources, the packet size, the rate at which they were sending and the simulation time. In these simulations, we wanted to investigate how the mobility affected the Essay No Simple Solution Problem protocols, so the Snow load that we offer is very low. We only use 15 CBR sources sending 64 bytes large packets with a rate of pricing 5 packets/s. Snow. The bandwidth of the inductive and deductive links are 2 Mbit. 39 5.3.2 Fraction of received packets 0.8 Fraction received packets 1 0.8 Fraction received packets 1 0.6 0.4 0.2 0.6 0.4 0.2 AODV-HELLO-MAC AODV-MAC AODV-HELLO DSR-eaves dropping DSR 0 0 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) 1 Fraction received packets 0.8 0.6 0.4 0.2 AODV-HELLO-MAC DSR DSDV 0 0 0.5 1 1.5 2 Mobility (m/s) Figure 13: 2.5 3 3.5 Mobility simulations - fraction of received packets. Essay. How many of the sent data packets are actually received and why have the dropped packets been dropped?
Of the new product pricing strategies different AODV versions, it can been seen in Figure 13 that both AODV versions that have MAClayer support are almost receiving all packets that are sent. AODV with both hello messages and White, MAC-layer support is slightly better than the version with only MAC-layer support. Personal Essays. The reason for Snow White this is the in macbeth same as mentioned earlier, the Snow White hello messages gets some prior knowledge of link breakages. AODV with only hello messages is however dropping a very large portion of the packets when the reflective essays mobility increases. Essay. This large fraction of dropped packets is of course not acceptable and the reason for these drops has to do with the interval of the hello messages. The interval between the hello messages and the number of allowed hello message losses are crucial for new product pricing strategies detection of link breakages. If the interval is Snow White decreased, link breakages are detected earlier, but it would also mean that the why is disposal of nuclear materials problem control overhead in the network increases. The issue here is to try to find optimal values for these parameters. The choice of these parameters is also very dependent on the behavior that is Snow White desired; a higher fraction of received packets, a high throughput, low delay or a low overhead. Why Is Waste Disposal Problem. The fraction of Essay received packets for the DSR versions is very large even for high mobility.
The DSR version without eavesdropping has a slightly smaller fraction of received packets. New Product Strategies. This difference is however so small that it is negligible. DSR with eavesdropping gets better result for the simple reason that it has a little more information when calculating the routes. White Essay. A reason for the higher fraction received packets for why is waste disposal of nuclear materials a serious problem DSR compared to AODV is that DSR allows packets to stay in the send buffer for Snow as long as 30 seconds, AODV only 8 seconds (our implementation). It must however be noted that the AODV draft  does not specify how long a packet is allowed to reflective, stay in the sendbuffer. When comparing these results with the Essay results for DSDV it can clearly be seen that a proactive approach is not acceptable at inductive, all when the Snow Essay mobility increases. The fraction received packets drastically goes down to 56-57 %. This value is however for a very large mobility factor (vehicles).
But the fraction of received packets is waste disposal of nuclear materials a serious not even 100 % when the mobility is 0, as for all other protocols. The reason for this is Essay that packets are sent before the routing tables have had enough time to converge and the packets are dropped. Essay No Simple To This. 40 The main reasons for dropping packets are that the Snow White Essay protocol is sending packets on a broken route that it thinks is valid and that packet in the buffers are dropped because of congestion and timeouts. At this low load we only have a small fraction of the on Poverty: No Simple Solution Multi-faceted packets that have been dropped because of collision. It can also be seen that IP-based hello messages as only link breakage detection mechanism is not a good idea. The results are very poor, even DSDV have slightly better results. Link layer feedback of link breakages informs the upper layer routing protocol is much quicker and Essay, it can therefore react immediately. 5.3.3 End-to-end delay AODV-HELLO-MAC AODV-MAC AODV-HELLO 0.14 0.12 Avg packet delay (seconds) 0.12 Avg packet delay (seconds) DSR-eaves dropping DSR 0.14 0.1 0.08 0.06 0.1 0.08 0.06 0.04 0.04 0.02 0.02 0 0 0 0.5 1 1.5 2 2.5 3 3.5 2.5 3 0 0.5 1 1.5 2 Mobility (m/s) 2.5 3 3.5 3.5 Mobility (m/s) AODV-HELLO-MAC DSR DSDV 0.14 Avg packet delay (seconds) 0.12 0.1 0.08 0.06 0.04 0.02 0 0 0.5 1 1.5 2 Mobility (m/s) Figure 14: Mobility simulations - delay. As seen in Figure 14, of the different AODV versions AODV with only hello messages has lowest delay on african and native american relations the data packets that are received. The reason for this is not that it finds routes faster or that the Snow White Essay routes are shorter or more optimal, instead AODV with only duncan, hello messages is the AODV version that gets significantly fewest packets through the network. Snow White. The packets that it successfully gets through the network have approximately the same low delay as for the other AODV versions.
The difference is that the other AODV versions have a portion of packets that have a higher delay (has been in african and native american a buffer a long time and still gets the White Essay packets through the network). This affects the average delay, which becomes larger. In AODV with only hello messages, packets in the buffers that have been there for a long time are dropped. The reason is that ADOV does not successfully find a new route for No Simple to this Multi-faceted those packets and because broken links are not detected fast enough, resulting in that a source can keep sending packets on a broken link believing that it is still working properly. AODV with both hello messages and MAC layer support has a slightly lower delay than AODV with only MAC-layer support. The reason for this is that as mentioned earlier, AODV with only MAC-layer support makes the protocol completely on-demand, it only detects link breakages when actually trying to send packets. Packets that are sent after this breakage is detected will have a higher delay, because they are buffered during the time it takes to Snow White Essay, find a new route.
AODV with both hello messages and Mac-layer support on american the other hand will get some prior knowledge of the link breakage and Snow White Essay, has a chance to find a new route before any new packets are sent. 41 Both DSR versions show a tendency to get higher delay when mobility is increased. The turning point comes at a mobility factor of duncan in macbeth approximately 1.0. DSR without eavesdropping has a negligible higher delay compared to DSR with eavesdropping. DSDV is the protocol that seems to have lowest delay in these results. Snow. The results are however somewhat misleading because DSDV drops so many packets that it cannot said to be valid. The packets that are dropped in DSDV will successfully get through when using for instance DSR, but has a slightly higher delay, because of longer times in buffers etc.
These higher delay packets will make the average delay higher for DSR. The same can be said for personal reflective AODV with only hello messages. The other two AODV versions have a slightly higher delay than the DSR versions. This has probably to do with the source routing concept of DSR. DSR gains so much information by the source routes that it will learn routes to Snow White, many more destinations than a distance vector protocol like AODV.
This will mean that while DSR already has a route for a certain destination, AODV would have to and deductive research, send a specific request for Snow White Essay that destination. The packets would in and deductive research the meanwhile stay in a buffer until a valid route is found. This will take some time and will therefore increase the average delay. In a packet based radio network without Quality of Snow Essay Service, the delays of the packets will vary much. The packets that do not have a route will be buffered until a route is duncan in macbeth found. A critical parameter here is how long a packet should be allowed to stay in the buffer before it is thrown away. If the packets are allowed to be in the buffer for Snow White Essay a long time, the following situation could happen: A packet is new product pricing strategies sent, but there does not exist any route to Snow Essay, that destination so the why is materials a serious packet is buffered and a route request is White Essay sent. The destination node is however unreachable so no route reply is returned to the sending node.
After a long time, the on Poverty: Solution to this destination node suddenly becomes reachable and the packet is sent. This packet will have a very large delay. Should this situation be allowed to happen? Should the packet be dropped from the White Essay buffer at duncan in macbeth, a much earlier stage or do we want all packets to get through the network, even though the Snow White delay can be very large. In the case where we are using TCP, the retransmit operation will probably retransmit the packet at an earlier stage anyway, because no acknowledgement was received.
The allowed time for why is waste materials problem packets to stay in the sendbuffer in DSR is 30 seconds and White Essay, only 8 seconds for AODV. If a packet is received 30 seconds after it was sent, this will increase the average delay to some degree. 5.3.4 End-to-end throughput 2.4 2.2 2.2 Throughput (Kbit/s) 2.6 2.4 Throughput (Kbit/s) 2.6 2 1.8 1.6 1.4 2 1.8 1.6 1.4 1.2 1.2 AODV-HELLO-MAC AODV-MAC AODV-HELLO DSR-eaves dropping DSR 1 1 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) 0 0.5 1 1.5 Mobility (m/s) 2.6 2.4 Throughput (Kbit/s) 2.2 2 1.8 1.6 1.4 1.2 AODV-HELLO-MAC DSR DSDV 1 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) Figure 15: Mobility simulations - throughput. 42 2 2.5 3 3.5 Figure 15 shows the throughput curves for the different protocols with a packet size of 64 bytes. It must however be mentioned that the curves in this case are only disposal, interesting from a relative view, as a comparison between the protocols. We have not tried to Essay, maximize the throughput, we have only to this Multi-faceted Problem, tried to determine the relative difference in throughput for the different protocols with respect to Snow White, the mobility factor and the specific load that we have used. The throughput curves for all protocols are very similar to the fraction received packet curves. This is logical because large packet drops will of course mean lower throughput. Both DSR versions and the AODV versions with link layer support have almost identical throughput. This throughput is and deductive research also approximately constant, it decreases somewhat when mobility is as high as 2.5-3.5. White Essay. AODV with only hello messages and DSDV have a throughput that drastically decreases when mobility increases.
AODV with only inductive and deductive, hello show a very poor result. The throughput curve drops almost immediately to half of what it is when mobility is Snow White 0. 5.3.5 Overhead 25000 1.8e+06 AODV-HELLO-MAC AODV-MAC AODV-HELLO 20000 1.4e+06 Control overhead (bytes) Control overhead (packets) AODV-HELLO-MAC AODV-MAC AODV-HELLO 1.6e+06 15000 10000 1.2e+06 1e+06 800000 600000 400000 5000 200000 0 0 0 0.5 1 1.5 2 Mobility (m/s) 2.5 3 3.5 0 25000 0.5 1 1.5 2 Mobility (m/s) 2.5 3 3.5 1.5 2.5 3 3.5 2.5 3 3.5 1.8e+06 DSR-eaves dropping DSR DSR-eaves dropping DSR 1.6e+06 1.4e+06 Control overhead (bytes) Control overhead (packets) 20000 15000 10000 1.2e+06 1e+06 800000 600000 400000 5000 200000 0 0 0 0.5 1 1.5 2 2.5 3 3.5 0 0.5 1 Mobility (m/s) 25000 1.8e+06 AODV-HELLO-MAC DSR DSDV AODV-HELLO-MAC DSR DSDV 1.6e+06 20000 1.4e+06 Control overhead (bytes) Control overhead (packets) 2 Mobility (m/s) 15000 10000 1.2e+06 1e+06 800000 600000 400000 5000 200000 0 0 0 0.5 1 1.5 2 Mobility (m/s) 2.5 Figure 16: 3 3.5 0 0.5 1 1.5 2 Mobility (m/s) Mobility simulations - overhead. Because the pricing strategies routing protocol need to Snow Essay, send control information to achieve the task of finding routes, it is interesting to why is waste disposal materials a serious problem, see how much control information that is actually sent for each protocol. Snow. There exists some sort of tradeoff between the byte overhead and disposal of nuclear, the number of control information packets sent. A large byte 43 overhead would of Snow Essay course mean a larger part of why is waste disposal of nuclear problem wasted bandwidth. Many small control information packets would however mean that the radio medium on which packets are sent is Snow Essay acquired more frequently. This can be quite costly in terms of power and and deductive research, network utilization. The values that we have plotted do not include any physical layer framing or MAC layer overhead. Snow White. We have only looked at the overhead at the IP-level. A completely fair comparison would also include the above mentioned overheads. We have chosen not to include these for the simple reason that the MAC layer can be different in a real life implementation.
We wanted to and native american, investigate the overhead generally, not the overhead that is dependent on particularly the IEEE 802.11 MAC protocol. The results are shown in Figure 16. The first column is overhead calculated in number of packets and Snow White, the second column is the byte overhead. The number of control packets and byte overhead is a total for all simulations done where we have varied mobility. Of the different AODV versions, it can be seen that the and native relations curves for the AODV versions that have link layer support are similar in White Essay appearance. Reflective. The difference of about 8000-9000 packets and 270000-290000 bytes that can be seen corresponds to Snow Essay, the hello packets. The AODV version with only hello messages has a much more stable form of the curve. The small rise that is visible is the triggered route replies that are sent when a link goes down and the new requests that are sent to personal reflective, find a new route during route failures.
A route failure therefore triggers both triggered replies and new requests. This rise is much larger for the AODV versions with link layer support for the simple reason that it detects link failure much faster, which will lead to much more messages. DSR does not include the data packets in Snow White Essay the number of Essay Multi-faceted Problem control packet calculations, only the extra byte overhead from these packets is included. Worth noting when observing the DSR versions is that the DSR version that does not use eavesdropping has approximately the Essay double amount of control overhead counted in number of messages and about 400000 bytes more of inductive and deductive research byte overhead than the DSR version with eavesdropping at the highest mobility 3.5. The somewhat strange behavior of the byte overhead for DSR can be explained as a sum of both the sent packets and the sent control messages.
As mobility increases, fewer packets will get through the network. Fewer packets mean less byte overhead in the source route of the White Essay packets. Increased mobility also means more topology changes, which will increase the duncan number of update messages. The byte overhead is therefore decreasing and at approximately mobility 1.5 the increase of control messages will cause the byte overhead to increase. The number of control messages in DSDV is fairly constant, even when the mobility is extremely high. Snow Essay. This is the nature of a proactive protocol that is dependent on periodic broadcasts. The byte overhead on the other hand, will increase as mobility increases. The reason for american relations this is that the amount of information sent in Snow White each update message will be larger as the amount of link changes increases. 5.3.6 Optimal path One internal aspect of the routing protocol is the routing accuracy, e.g. how good the actual routes are compared to personal reflective essays, the optimal routes. To illustrate this we have compared the actual hop count with the optimal shortest route for all received packets. We have then, for each protocol, calculated how large fraction the received packets that have been routed through the optimal route, a route with hopcount that is one larger than the Snow White optimal, a route with hopcount that is two larger than the optimal and reflective, so on.
The result is shown in Table 8. The results are the Essay total results for all simulations done with varying mobility. Duncan. To better illustrate the difference between some of the protocols, we have also plotted the Snow White Essay results for one AODV version, one DSR version and compared it with the only proactive protocol DSDV. In Macbeth. It can clearly be seen in Figure 17 that DSDV is the protocol that has the highest degree of Snow optimality, almost 90 % of the received packets have been routed with optimal hop count. The AODV and DSR versions are almost identical. AODV is slightly better. New Product Pricing. This difference is however so small that it can neglected. The difference between the Snow White Essay different DSR versions is quite large and can be explained with the extra information that DSR with eavesdropping has when calculating routes. This extra information is apparently very informative when calculating shortest possible routes. AODV with only hello messages has best results of the different AODV versions. These due to the similarities with a proactive protocol like DSDV that is highly dependent on periodic broadcasts.
Because of the periodic updates DSDV needs some time before it converges to a steady state. This happens when we have high movement with a lot of new product topology changes. Most of the packets that are sent during this time are dropped and the rest of Snow White Essay them get a little higher hopcount. Pricing Strategies. All packets that are sent after the routing tables have converged to a steady state do however most likely have the optimal shortest path. Snow White. AODV with only hello messages have a similar behavior. Link breakages are dependent on the hello messages. Personal Reflective Essays. This will mean that high movement and frequent topology changes will lead to Essay, many packet 44 drops during this time.
The packet that successfully gets through the network have done this during times when the network is somewhat stabile 1 AODV-HELLO-MAC DSR DSDV Packets (%) 0.8 0.6 0.4 0.2 0 0 2 Figure 17: 4 6 Nr of hops from optimal 8 10 Mobility simulations - optimal path difference. Because both DSR versions and the AODV versions with link layer support gets significantly more packets through the in macbeth network when the number of topology changes is large, they will have a little lower fraction of packets that have a optimal route. In times of frequent movement it is easy to get a route that at first is Snow Essay optimal and then the in macbeth moment later is 1-2 hops longer than another route that become the optimal route. The protocols will keep sending packets on the route that at first was optimal. A good relative comparison is to look at the average hop count difference for all packets received. DSDV has the Essay smallest average with a hopcount at only 0.13 hops from the optimal path. Table 8: Protocol AODV 1 AODV 2 AODV 3 DSR 1 DSR 2 DSDV 0 79.1% 55.9% 68.4% 81.1% 63.2% 88.7% Optimal path difference for and deductive all protocols.
Number of hops from optimal path (% packets) 1 2 3 4 5 6 14.8% 3.68% 1.08% 0.30% 0.55% 0.06% 29.9% 9.04% 2.62% 1.09% 0.56% 0.20% 23.0% 5.37% 1.48% 0.84% 0.47% 0.14% 15.3% 2.73% 0.54% 0.13% 0.08% 0.01% 26.6% 7.21% 2.21% 0.56% 0.13% 0.05% 10.6% 0.59% 0.06% 0.00% 0.00% 0.00% 45 7 0.06% 0.38% 0.04% 0.02% 0.03% 0.00% Average 0.292170 0.682837 0.459423 0.234429 0.512004 0.126577 5.3.7 Summary mobility simulations The protocols that have link layer support for Snow link breakage detection will be much more stable. The fraction of packets received for these protocols is almost constant at 95 % even when mobility increases. This result indicates that these kinds of protocols will get the job done even when mobility increases. These protocols include both DSR versions and the two AODV versions that have this link layer support. Protocols that are highly dependent on new product strategies periodic broadcast show a rather poor result, only little more than 50 % of the packet are received when mobility is increased. Snow Essay. Because DSR is research a source routing protocol it is always interesting to see how much overhead this kind of protocol will have. Snow. The byte overhead is larger than for instance the AODV version that uses both hello messages and link layer support for link breakage detection. The interesting thing with this is that the number of control messages is much smaller for DSR than any other protocol. This is reflective interesting because this means that an approach that uses a source routing based approach to Essay, find routes combined with a destination vector approach for duncan in macbeth sending data packets could be desirable. 5.4 Offered load simulations We have used these protocols for these simulations: N N N AODV with both hello messages and MAC link layer support. White Essay. DSR without eavesdropping DSDV We only used the more realistic version of new product strategies both AODV and DSR, for the same reason as mentioned in the previous section.
5.4.1 Setup The offered load simulations where done by Snow White varying the load that we offer the network. New Product Pricing Strategies. We had mainly three parameters to adjust the Snow Essay offered load: N N N Packet size Number of CBR flows Rate at which the flows are sending The mobility simulations that we have done used a packet size of 64 bytes, a rate of 5 packets/s and 15 CBR flows. Why Is Materials Problem. This is Snow Essay a fairly moderate offered load, so for the offered load simulations, we wanted to investigate how the protocols behave when the load was increased. We could increase the packet size or the number of CBR flows, but the parameter that best describes the load is the rate at which we are sending. By only increasing the rate for the CBR flows, the load for reflective each flow will increase. This also gives some hints of how large the throughput can be. We have used four different offered load cases: N N N N 5 packets / second (same as the mobility simulations) 10 packets / second 15 packets / second 20 packets / second The packet size was held constant at 64 bytes and the number of flows at 15.
We used the same randomized scenario files as in Snow White the mobility simulations. The same communication file was also used, with the why is waste disposal a serious exception that we changed the rate for Snow Essay the CBR sources. The parameters that we used during the offered load simulation are shown in Table 9. Personal Essays. 46 Table 9: Parameters used during offered load simulations. Parameter Transmitter range Bandwidth Simulation time Number of Snow White nodes Pause time Environment size Traffic type Packet rate Packet size Number of and deductive research flows Value 250 m 2 Mbit 250 s 50 1s 1000x1000 m Constant Bit Rate 5 packets/s 64 byte 15 5.4.2 Fraction of received packets 0.8 Fraction received packets 1 0.8 Fraction received packets 1 0.6 0.4 0.2 0.6 0.4 0.2 AODV 5 pkt/s AODV 10 pkt/s AODV 15 pkt/s AODV 20 pkt/s DSR 5 pkt/s DSR 10 pkt/s DSR 15 pkt/s DSR 20 pkt/s 0 0 0 0.5 1 1.5 2 Mobility (m/s) 2.5 3 3.5 1 1.5 2 Mobility (m/s) 2.5 3 3.5 0 0.5 1 1.5 2 Mobility (m/s) 2.5 3 3.5 1 Fraction received packets 0.8 0.6 0.4 0.2 DSDV 5 pkt/s DSDV 10 pkt/s DSDV 15 pkt/s DSDV 20 pkt/s 0 0 0.5 Figure 18: Offered load simulations - fraction of received packets. At only 5 packets/s both AODV and DSR are rather constant, the fraction of received packets is only decreasing slightly when mobility increases (Figure 18). At 10 packet/s we can see that the fraction received packets is decreasing much faster when the Snow White Essay mobility factor is and deductive research greater than 2. White Essay. At 15 packets/s and 20 packets/s both AODV and DSR are dropping a large fraction of the why is waste materials packets. At the highest mobility and a rate of 20 packets/s, only 50-60 % of the sent packets are received. Snow White. The reason is more collisions in the air and congestion in essays buffers.
The results for AODV and DSR are fairly similar at Snow, a packet rate of 5 packets/s and reflective essays, 10 packets/s. At data rates of 15 packets/s and 20 packets/s, AODV shows a better result than DSR. At these rates the protocols are however dropping a large fraction of the packets, even at White Essay, a mobility factor of inductive research 0. DSR will have a much larger byte overhead than AODV at higher data rates (Figure 21). Snow White. The reason for this is the source route in african and native relations each data packet. This also increases the load on the network and Snow White, causes more packets to waste materials a serious, be dropped; thus AODV will get more packets through the network.
47 DSDV is dropping a large fraction of the White Essay packets already at the lowest data rate 5 packets/s. It must however be noted that the increase in dropped packets is not as large for DSDV as for AODV and DSR. In Macbeth. At the highest data rate, DSDV is almost as good as DSR. 5.4.3 End-to-end delay 0.7 0.7 AODV 5 pkt/s AODV 10 pkt/s AODV 15 pkt/s AODV 20 pkt/s 0.6 0.5 Avg packet delay (seconds) Avg packet delay (seconds) 0.6 DSR 5 pkt/s DSR 10 pkt/s DSR 15 pkt/s DSR 20 pkt/s 0.4 0.3 0.5 0.4 0.3 0.2 0.2 0.1 0.1 0 0 0 0.5 1 1.5 2 2.5 3 3.5 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) Mobility (m/s) 0.7 DSDV 5 pkt/s DSDV 10 pkt/s DSDV 15 pkt/s DSDV 20 pkt/s Avg packet delay (seconds) 0.6 0.5 0.4 0.3 0.2 0.1 0 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) Figure 19: Offered load simulations - average delay. The delay is also affected by high rate of CBR packets (Figure 19). The buffers becomes full much quicker, so the packets have to stay in the buffers a much longer period of White Essay time before they are sent. This can clearly be seen at the highest rate 20 packets/s. The high degree of personal reflective essays packet drops, even at mobility 0 makes the delay high already from the start.
DSR has a much lower delay compared to AODV. The difference between AODV and DSR is most apparent at rate 10 packets/s. Snow Essay. DSDV has the lowest delay of them all. New Product Strategies. This is Essay however an effect from the large fraction of packet drops that DSDV has, compared to DSR and AODV. The increase in delay for DSDV also comes from the increased time that the packets must stay in the buffers. The high delay at a mobility factor of 0-1 and a data rate of in macbeth 20 packets/s that can be seen for all protocols is White a result of the personal extremely high data rate and the low mobility. White. The high data rate will fill up the american buffers very quickly. The low mobility will mean that already found routes are valid for a much longer time period. Snow White Essay. This means that found routes can be used for why is a serious more packets.
Even the Snow White packets that have stayed in the buffer for a long time have a chance to get through. When mobility increases, more routes will become invalid and new requests are necessary. While the requests are propagating the network in search for a new route, buffers will get full and packets are dropped. These packets are the packets that have stayed in the buffers for the longest time and inductive, therefore the delay will decrease. The increase in mobility actually results in a load balancing of the traffic between the nodes; hot spots are “removed” due to Essay, mobility. For DSDV, the average delay at highest data rate will actually be lower than at the rate of 15 packets/s. This is personal essays a little strange but has probably something to do with the Snow Essay fact that DSDV only uses a buffer that only waste disposal problem, has room for 5 packets per flow.
At the White rate of 15 packets/s and 20 packets/s, when mobility starts to get so high that the topology changes frequently, only 40-60 % of the packets gets through the network. These 48 topology changes means that the protocol needs more time to converge before the inductive packets can be sent. The buffers will therefore be congested almost all the time so the Snow White Essay packets that actually get through have approximately the same the delay. African American Relations. 5.4.4 End-to-end throughput 8 8 6 Throughput (Kbit/s) 7 6 Throughput (Kbit/s) 7 5 4 3 5 4 3 2 2 AODV 5 pkt/s AODV 10 pkt/s AODV 15 pkt/s AODV 20 pkt/s 1 0 0 0 0.5 DSR 5 pkt/s DSR 10 pkt/s DSR 15 pkt/s DSR 20 pkt/s 1 1 1.5 2 Mobility (m/s) 2.5 1.5 2.5 3 3.5 0 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) 8 7 Throughput (Kbit/s) 6 5 4 3 2 DSDV 5 pkt/s DSDV 10 pkt/s DSDV 15 pkt/s DSDV 20 pkt/s 1 0 0 0.5 1 2 3 3.5 Mobility (m/s) Figure 20: Offered load simulations - average throughput. At low CBR rates the throughput of Essay DSR and AODV is No Simple to this Multi-faceted Problem unaffected of the mobility (Figure 20), it stays constant at 2,5 Kbit/s. White Essay. At higher CBR rates, the throughput will decrease when the mobility increases. This can already be seen at CBR rate 10 packet/s.
The decrease at CBR rate 10 packets/s is however very small. At rate 15 packets/s and 20 packets/s the american throughput decreases very much for all protocols. This is however an effect from the large fraction of dropped packets. The result for AODV is White Essay slightly better than for DSR. It must however be noted that the offered load definition that we use only personal reflective, includes the rate at which we are sending packets with; no control packets are included in this definition. The same applies for the throughput, only the data packets are included in the calculations of Essay throughput. African. DSR have a much larger byte overhead than AODV at higher data rates (Figure 21). This also increases the load on the network and causes more packets to be dropped; thus AODV will have a better throughput at White Essay, higher data rate.
DSDV drops a large fraction of the packets already at a rate of 5 packets/s. Pricing Strategies. This can be seen in the small decrease in Snow White the throughput at rate 5 packets/s. The throughput decreases more and more as the inductive research rate increases. 5.4.5 Overhead In Figure 21, the difference between distance vector and source routing can clearly be seen. The byte overhead for DSR is much larger than AODV even at low data rates and Snow White Essay, the difference becomes larger when the CBR rate increases. At CBR rate 20 packets/s, the byte overhead for DSR is more than the and native american relations double than for White AODV. The reason for the larger byte overhead for DSR is of course the new product pricing strategies source route in each packet. The 49 number of Essay control messages is though smaller for DSR. This is the other characteristic for source routing, it learns all routes in and deductive research the source route and Snow Essay, therefore does not need to and deductive, send as many route requests. The reason for the increase in number of control packets is the Essay MAC-layer support. The increase in rate means that the reflective MAC-layer will detects link failures much faster.
This means that the Essay triggered RREPs are sent much earlier also causing the source node to send out a new request much earlier. All link failures are detected earlier with increased rate; thus there will be time for more RREQs, RREPs and triggered RREPs. 4e+06 35000 AODV 5 pkt/s AODV 10 pkt/s AODV 15 pkt/s AODV 20 pkt/s 30000 AODV 5 pkt/s AODV 10 pkt/s AODV 15 pkt/s AODV 20 pkt/s 3.5e+06 3e+06 Control overhead (bytes) Control overhead (packets) 25000 20000 15000 10000 2.5e+06 2e+06 1.5e+06 1e+06 5000 500000 0 0 0 0.5 1 1.5 2 Mobility (m/s) 2.5 3 0 3.5 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) 35000 DSR 5 pkt/s DSR 10 pkt/s DSR 15 pkt/s DSR 20 pkt/s 30000 4e+06 3e+06 Control overhead (bytes) 25000 Control overhead (packets) DSR 5 pkt/s DSR 10 pkt/s DSR 15 pkt/s DSR 20 pkt/s 3.5e+06 20000 15000 2.5e+06 2e+06 1.5e+06 10000 1e+06 5000 500000 0 0 0.5 1 1.5 2 2.5 3 0 3.5 0 0.5 1 Mobility (m/s) 1.5 2 2.5 3 3.5 Mobility (m/s) 4e+06 DSDV 5 pkt/s DSDV 10 pkt/s DSDV 15 pkt/s DSDV 20 pkt/s 35000 DSDV 5 pkt/s DSDV 10 pkt/s DSDV 15 pkt/s DSDV 20 pkt/s 30000 3.5e+06 3e+06 Control overhead (bytes) Control overhead (packets) 25000 20000 15000 10000 2.5e+06 2e+06 1.5e+06 1e+06 5000 500000 0 0 0 0.5 1 1.5 2 Mobility (m/s) 2.5 Figure 21: 3 0 3.5 0.5 1 1.5 2 2.5 3 3.5 Mobility (m/s) Offered load simulations - overhead. The amount of essays control information in DSDV is White not affected to any great extent by american relations the data rate for the CBR packets. Snow Essay. By looking at and deductive, Figure 21 it looks like the Snow Essay number of control packets is exactly the same for personal all data rates, but there is actually a small difference. The number of control packets is actually a little smaller when the rate is White Essay 20 packets/s. This difference is about 80 packets.
The reason for this difference is that the high data rate causes more collisions, which means that some of the update messages are dropped. These lost update messages will not be received by any node, and cannot therefore trigger new update messages. New Product Strategies. This means that when the next update message actually is received a much larger update message has to be sent, thus we can see a slight increase of Snow White Essay byte overhead when the rate increases. But when the mobility increases more and more packets will be dropped. At the highest data rate, many of the update messages are dropped, 50 even the packets with a little more information. This causes the new product pricing byte overhead for DSDV at higher data rates not to increase to the same extent as for DSDV with lower data rates. 5.4.6 Optimal path Figure 22 illustrates the difference in Snow Essay hopcount from the optimal hopcount at a CBR rate of 20 packets/s. It is the result for research all simulations done at this rate. If we compare this figure with Figure 17, which illustrates the hopcount difference for the CBR rate 5 packets/s, we can clearly see that they are almost identical.
The rate does not affect the number of hops that the Essay packets actually need to travel from source to waste disposal of nuclear materials a serious, destination. 1 AODV 20 pkt/s DSR 20 pkt/s DSDV 20 pkt/s Packets (%) 0.8 0.6 0.4 0.2 0 0 2 Figure 22: 4 6 Nr of hops from optimal 8 10 Offered load simulations – optimal path. 5.4.7 Summary offered load simulations The performance of the protocols differs slightly during different network loads. The most apparent difference is the byte overhead. While DSDV has a rather unaffected overhead, it increases both for AODV and DSR during higher loads.
A higher sending rate causes the Snow Essay protocol to detect broken links faster, thus reacting faster. This leads to a slight increase in reflective essays control packets, which also affects the byte overhead. The most apparent is the increase in Snow White Essay DSRs overhead as we increase the send rate. Since each data packet contains a source route, the inductive and deductive byte overhead increases dramatically. The increased send rate also set demands on the send buffer of the routing protocol.
Congestion occurs and packets are dropped. The faster a routing protocol can find a route, the White less time the duncan packets have to spend in buffers, meaning a smaller probability of packet drops. 51 5.5 Network size simulations We did simulations on Snow White Essay some of the why is waste protocols and varied the Snow White number of nodes that participated in the network. We decreased the number of in macbeth nodes to 35 and 25 nodes. The decrease in number of nodes basically meant that the White connectivity also decreased; each node had fewer neighbors.
The results from research these simulations did not give any new information regarding the performance of the protocols. The relative difference between the protocols was the same. White Essay. Decreased connectivity meant of and deductive research course that we did not get as many packets through the network as in White Essay the mobility simulations, but it must however be noted that the dependency between the scenarios and results are much larger in in macbeth the network size simulations. The worst results for each protocol happened when the mobility was 0. This may sound strange, but the reason for the bad result when the nodes is standing still is the randomized scenarios. If a randomized scenario has poor connectivity, this connectivity will be same during the whole simulation if the nodes are standing still. The nodes are not moving and cannot therefore affect the connectivity. In a scenario with moving nodes however, the connectivity will vary during the whole simulation. Snow. So even if a node is waste a serious problem unreachable from the beginning, there is still a chance that it will be reachable some time later. 5.6 Realistic scenarios 5.6.1 Setup The randomized simulations we have done, gives a very good general picture of how the protocols behaves in respect to Essay, certain parameters, such as mobility, size and network load. This kind of simulations also has some problems: N N N It is hard to identify situations in reflective which the protocols fail or have problems It has no connection to a real life situation. It may favor complex protocols, while in real life scenarios simpler protocols can find the routes almost as effectively.
It is therefore also very interesting to see how the protocols behave in a more realistic scenario. Snow White. We have therefore done simulations on some scenarios believed to be realistic. Reflective Essays. The realistic scenarios do not give a full picture of how the protocols behave generally. Instead they give some sense of weak points in the protocols. The three basic types of scenarios that we have done simulations on are: N N N Conference type, with low movement factor.
Event coverage type, with fairly large movement factor. Could for instance be reporters trying to interview politicians. Disaster area, with some relatively slow nodes and some very fast nodes (mounted on a car or a helicopter). Snow. The environment size is 1500 x 900 meters for all realistic scenarios. This size is scaled according to the range of the transmitters. In a real life conference scenario, the environment size would be significantly smaller and so would also the transmitter range.
The same thing would apply for the speed of the people moving around. The speed is also scaled to 10 m/s. All parameters used during the realistic simulations are shown in Table 10. Inductive. 52 Table 10: Parameters used during realistic simulations. Snow. Parameter Transmitter range Bandwidth Simulation time Number of nodes Environment size Traffic type Packet rate Packet size Speed of a human Speed of a mobile node mounted on new product strategies a vehicle Value 250 m 2 Mbit 900 s 50 1500x900 m Constant Bit Rate 4 packets/s 512 byte 1 m/s 20 m/s 5.6.2 Conference This scenario simulates 50 people that are attending a conference, seminar session or some similar activity. It involves communication between some of the people. Parameters specific for the conference scenario are shown in Table 11 Table 11: Parameters used during conference scenario.
Parameter Number of CBR sources Number of receivers Number of flows Value 2 6 6 The scenario is characterized by: N N N N N Low mobility factor, 10 % of the nodes are moving during any period of White time. Links are long lasting and involves many hops. In Macbeth. The traffic is concentrated to a few nodes, typically only the Snow Essay speaker. Few obstacles which are far apart. And Deductive. Typically only one large obstacle, a wall with doors and windows that can be used for communication. Relatively large interference from other nodes, due to the concentration of transmitting nodes. This can in some cases lead to Essay, local congestion. The scenario basically tests the protocols: N N N Ability to why is of nuclear problem, respond to local changes for Snow White long links. Ability to Essay on Poverty: to this Multi-faceted, cope with large concentration of traffic.
Message overhead with low mobility factor. Figure 23 shows how the White scenario was designed and created with ad-hockey. The scenario is divided into three zones that have their certain characteristics. N N N Zone 1 - Speaker zone: The speaker moves back and forth. This changes the essays closest neighbor in the audience.
Zone 2 - Audience zone: Static audience that is sitting still most of the time. Very seldom does a node go outside to White, return a certain amount of time later. This will probably result in a link breakage of and native american relations a longlasting link. Snow. Zone 3 - Outsider zone: Outsiders behind a wall that are trying to establish a connection between the speaker and in macbeth, each other. White Essay. 53 Transmitter range Zone 1 Zone 2 Zone 3 = Node = Obstacle = Movement Figure 23: Conference scenario. The results for this scenario are shown in Table 12 and Table 13.
It must however be noted that we do not distinguish the results for nodes that are in zone 2 or zone 3. The calculated mobility factor for reflective essays this scenario is very low. All protocols except DSDV and Snow White Essay, the AODV version that only essays, uses hello messages show quite good performance, delivering between 92-99% of the packets with an average throughput between 14.8 – 15.7 Kbit/s. Essay. DSDV delivers only 75.6% of the packets with an average throughput of 12.1 Kbit/s and the AODV version with only hello messages delivers 89.3 % of the packets, with a throughput of 14.3 Kbit/s. This shows that an ad-hoc routing protocol must quickly adapt to new product, link changes even for White long lasting routes as in this case where mobility is very low. Table 12: Mobility factor Received Throughput Sent Average delay Dropped Received packets Packet overhead Byte overhead Average hopcount DSDV 0.0439350 75.6% 12.1 Kbit/s 21510 0.052 s 5250 16260 44054 6406036 5.32 Conference simulation results. DSR - 1 0.0439350 97.1% 15.55 Kbit/s 21510 0.210 s 614 20896 3129 3689865 5.73 DSR - 2 0.0439350 98.0% 15.7 Kbit/s 21510 0.23 s 422 21088 4109 4093220 5.79 54 AODV - 1 0.0439350 89.3% 14.30 Kbit/s 21510 0.26 s 2298 19212 43881 1660020 6.62 AODV - 2 0.0439350 92.3% 14.79 Kbit/s 21510 0.29 s 1644 19866 14537 610884 6.53 AODV - 3 0.0439350 94.0% 15.00 Kbit/s 21510 0.39 s 1376 20134 54677 2112716 6.45 Both versions of DSR have the lowest packet overhead in african and native american relations this scenario, while all versions of AODV show the lowest byte overhead. The large byte overhead for White Essay DSR has to duncan in macbeth, do with the fairly large amount of traffic and that the routes have an average hopcount that is as large as 5-6 hops.
As can be seen in Table 13. DSDV fails to deliver 3599 packets because of route failures. This is due to the slow response time when links go down and the time it takes to find new routes. A lot of packets will be sent using a route that the Essay protocol thinks is valid, while in fact the african and native american relations route is broken and White Essay, the packets are dropped. Also a lot of waste problem packets are dropped in the interface queue. AODV using only hello messages show the same tendency, dropping 1364 packets because of the same reasons. It is however fewer packets than for DSDV. This has to do with the time between the Essay HELLO messages. The less time between the messages, the faster can the protocol react to duncan, broken links and avoid dropping the packets. In general, most of the packets are dropped in the sendbuffer. Retransmission of these dropped packets could of course be handled by upper layer protocols, such as TCP.
Table 13: Cause for drop Sendbuffer Route failures ARP Interface queue End of simulation DSDV 3599 74 1567 10 Packet drops in conference scenario. Snow. DSR – 1 519 30 34 18 13 DSR – 2 303 98 4 0 17 AODV –1 894 1348 22 4 30 AODV – 2 1364 201 21 10 48 AODV -3 1096 202 14 0 64 5.6.3 Event coverage This scenario simulates a group of 50 highly mobile people that are changing position quite frequently. It could for instance represent a group of inductive and deductive reporters that are covering a political event, music concert or a sport contest. In real life it would be nearly impossible to establish a wired network between the reporters, but they must be in constant communication with each other, enabling a fast reaction. Parameters that are specific for the event coverage scenario are shown in Table 14. Table 14: Parameters used during event coverage scenario. Parameter Number of CBR sources Number of receivers Number of flows Value 9 45 45 The scenario is Snow characterized by: N N N N N Rather high mobility factor. Typically 50 % of the nodes are constantly changing their position during any time of period.
Every now and then the nodes tend to cluster. Links involve a few hops and relatively short-lasting. Traffic is spread all over the place. Many obstacles. Nodes can usually only communicate with a few nodes. This will lead to new product strategies, a low interference from the other nodes, except for the moments of Snow clustering. Personal. 55 The scenario tests the protocols: N N Ability to Snow, respond to fast link changes and fluctuating traffic. Message overhead with constant topology updates. Figure 24 shows how the scenario was designed. 50 % of the inductive and deductive research nodes are moving randomly with a constant speed of 1 m/s. Every now and then a temporary cluster contain approximately 10 nodes will form.
These clusters remain static for Essay a certain amount of time. Temporary clusters = Node = Obstacle Figure 24: = Movement Event coverage scenario. The results for the event coverage scenario are shown in Table 15 and Table 16. As Table 15 shows, the african and native american relations two protocols that has the White Essay lowest fraction of packets received are DSDV and the AODV version that entirely relies on feedback from link-layer. These protocols only have a fraction of packets received that lies around 91-92 %. For all other protocols/versions this value is at least 94 %. The mobility factor for the scenario is 0.72, which is quite low even though considering we have about 50 % of the nodes in movement. The nodes are however only moving with a speed of 1 m/s. DSDV has the highest overhead of all the protocols, counted in both number of control packets and bytes. DSR both with and without eavesdropping have a very low overhead. It must however be noted that the traffic load in this scenario is very low and most of the communication is taking place in a very small area, thus leading to a very low average hopcount of approximately 1.5 for personal all protocols. In this scenario, AODV with only hello message shows better results than AODV with only link-layer support and Snow Essay, the reason is that the hello messages makes it possible to keep track of neighbors. Most of the communication is taking place within clusters, so to new product strategies, know the neighbors will probably mean that we will not have to make as many requests.
The topology of the network is changing quite frequently. This causes a protocol like DSDV to have a very large overhead. The communication however, take mostly place within the clusters. This makes the job for the on-demand-based protocols much easier. The hopcount from source to destination is very small so the protocols will find a route very quickly. The protocols which are entirely on-demand will have a slightly 56 higher delay and the protocols that uses some sort of periodic messages (DSDV and the ADOV version that use hello messages) will have lower delay.
Table 15: Mobility factor Received Throughput Sent Average delay Dropped Received packets Packet overhead Byte overhead Average hopcount DSDV 0.721611 91.4% 14.75 Kbit/s 4500 0.075 s 385 4115 42415 10578764 1.46 hops Event coverage simulation results. Essay. DSR – 1 0.721611 97.5% 15.68 Kbit/s 4500 0.138 s 111 4389 1056 141196 1.53 hops DSR – 2 0.721611 97.7% 15.71 Kbit/s 4500 0.140 s 102 4398 1354 158420 1.57 hops AODV – 1 0.721611 94.5% 15.33 Kbit/s 4500 0.024 s 245 4255 31342 1137752 1.55 hops AODV – 2 0.721611 92.2% 14.89 Kbit/s 4500 0.214 s 352 4148 2722 117904 1.75 hops AODV – 3 0.721611 95.1% 15.36 Kbit/s 4500 0.015 s 219 4281 31443 1142180 1,55 hops Table 16 shows that most of the packets are dropped due to route failures and in those cases where there exists a sendbuffer, congestion/time-out in waste of nuclear materials problem the sendbuffer. AODV that only White, uses link-layer support (AODV 2) has most of the dropped packets due to duncan, failed ARP requests and Snow, DSDV drops most of its packets at the interface queue. Personal Essays. Table 16: Cause for drop Sendbuffer Route failures ARP Interface queue End of simulation DSDV Packet drops in event coverage scenario. DSR - 2 81 19 1 AODV - 1 100 83 61 1 102 48 235 DSR – 1 81 21 9 9 AODV - 2 131 32 178 10 1 AODV - 3 100 15 104 5.6.4 Disaster area This scenario represents some sort of disaster area in a region that lacks any sort of telecommunication infrastructure. It could for Snow White instance represent a natural disaster or a large rescue operation. Pricing. Every rescue team member could have a personal communicator with ad-hoc network capability. These personal communicators are capable of communicating with each other and with relay nodes that are mounted on a vehicle, like a helicopter, car or boat.
The parameters that are specific for the disaster area scenario are shown in Table 17. Snow White Essay. Table 17: Parameters used during disaster area scenario. Parameter Number of CBR sources Number of receivers Number of waste materials problem flows 57 Value 38 87 87 The scenario is characterized by: N N N N N N A node movement, where approximately 95 % of the nodes are moving slightly, while the remaining 5 % are changing their position very often. Network partitioning now and then. Long and short lasting links that only are a few hops.
Traffic that is spread all over the nodes. Snow White. Many obstacles. Low interference from the other nodes. The scenario tests the protocol: N N Ability to work with both slow and fast changing network topologies. Pricing. Ability to cope with network partitioning. Figure 25 shows how the scenario was designed. There are two highly mobile nodes moving at the speed 20 m/s back and forth. There are also three separate subnetworks that can connect to Snow Essay, each other through the new product pricing strategies relays mounted on the highly mobile nodes. Within each subnetwork, the Snow White movement is randomized at speed 1 m/s.
Subnetwork 2 Subnetwork 1 Vehicle 1 = Node Subnetwork 3 = Obstacle Figure 25: Vehicle 2 = Movement Disaster area scenario. The results for the disaster area scenario are shown in pricing strategies Table 18 and Table 19. The calculated mobility factor for this scenario is quite high. Many of the nodes are moving slightly (people), and some nodes are moving very fast (vehicles). The protocols that show the Snow White best results in personal this scenario are the purely reactive approaches, that is Essay AODV using both hello messages and MAC support and in macbeth, DSR with eavesdropping. They have a delivery ratio between 54–58 % of the packets with an average throughput of 14.1 – 14.8 Kbit/s. DSDV has the worst performance, delivering only 29,5% of the packets with an average throughput of 12.42 Kbit/s. A delivery ratio of only 58 % for the best protocol may sound like a terrible ratio, but because of Snow network partitioning, it is hard for any protocol to successfully deliver more packets than that. 58 DSDV show the lowest delay, but this is Essay No Simple due to Snow White Essay, the low delivery ratio. Materials A Serious. All versions of AODV keep an average delay between 0.89 – 1.05 seconds, while the DSR versions lie between 1.19 – 1.25 seconds. Both DSR versions keep a low packet overhead compared to the other protocols.
The byte overhead is however twice as large for DSR compared to White Essay, AODV. As expected, DSDV uses the strategies shortest paths with an average of 3.42 hops. The other protocols has an average hopcount of 5.0-5.2 hops. Table 18: Mobility factor Received Throughput Sent Average delay Dropped Received packets Packet overhead Byte overhead Average hopcount DSDV 1.154619 29.5% 12.42 Kbit/s 29616 0.196 s 20867 8749 41402 6497476 3.42 hops Disaster area simulation results. DSR – 1 1.154619 58.0% 14.79 Kbit/s 29616 1.252 s 12440 17176 27048 4880992 5.01 hops DSR – 2 1.154619 54.50% 14.43 Kbit/s 29616 1.187s 13464 16152 30692 5137148 5.16 hops AODV – 1 1.154619 48.0% 13.07 Kbit/s 29616 0.888 s 15382 14234 61557 2426164 5.23 hops AODV – 2 1.154619 52.2% 13.49 Kbit/s 29616 1.052 s 14161 15455 50686 2426164 5.24 hops AODV – 3 1.154619 54.0% 14.09 Kbit/s 29616 0.988 s 13635 15981 77311 3096228 5.26 hops DSDV drops a lot of Snow Essay packets because of new product strategies route failures. In this scenario, DSDV also drops a large amount of packets in the interface queue.
One large cause for drops in the other protocols, lies in the sendbuffer. Snow White Essay. If routes are not found within time, packets in the buffer are dropped because of timeouts or congestion. Another large cause for packet drops is route failures. This scenario is american relations very interesting and Snow Essay, should be investigated further, especially for the AODV protocol. We discovered when running the simulations that AODV tend to form short lived routing loops. Reflective Essays. Since the author claim that this protocol should be loop free at all times, one possible cause for Snow White this might be invalid use of the on Poverty: No Simple to this Problem sequence numbers or the fact that sequence numbers are unsynchronized during network partitioning. Very few packets were dropped because of this (less than 5). Another interesting thing with this scenario is that all main nodes send traffic both ways to Snow White Essay, each other.
This causes AODV to respond to in macbeth, requests with temporary routes set up by other requests. Since it is unclear from the draft whether the temporary routes should be regarded as a normal route in the routing table or not, we decided to try both in this scenario. By only allowing RREPs to use the Essay temporary routes, and by duncan in macbeth not allowing a node to respond to a RREQ with a temporary route, the routing loops could be avoided. However, the performance of the protocol decreased. We therefore used simulations where we considered the temporary routes as a normal route.
Table 19: Cause for drop Sendbuffer Route failures ARP Interface queue End of simulation DSDV 15853 479 4528 7 DSR – 1 10033 1990 35 3 1 Packet drops in Snow Essay disaster area. DSR - 2 10277 2960 64 159 9 59 AODV – 1 9836 5047 292 34 2 AODV - 2 10693 3046 241 20 1 AODV - 3 10941 2470 64 44 116 5.6.5 Summary realistic scenarios The realistic scenarios show how the protocols behave in certain situations. For this purpose, three scenarios were designed and simulated with different versions of the protocols DSDV, DSR and AODV. DSR show the best performance results overall. If source routing is undesirable, another good candidate is AODV with only No Simple Solution to this Multi-faceted, MAC layer support.
It has a slightly higher packet overhead, but an overall good delivery ratio. 5.7 Observations The protocols that we have worked with most are AODV and Snow White Essay, DSR, thus we have observed some important differences for these protocols, that in some way affect the performance of the inductive research protocols. 5.7.1 Ability to find routes AODV To illustrate AODVs ability to Snow, find routes, we use a simple scenario (see Figure 26). Why Is Disposal Of Nuclear A Serious Problem. The scenario consists of four nodes A, B, C and D connected to each other. A C D B Figure 26: Simple example scenario. Node A needs a route to node D. No data has been sent earlier, thus the Essay only routes known to the AODV protocol are the different neighbors in the scenario. This is and deductive research because AODV uses hello messages to keep track of the neighbors of Snow Essay a node. Essay No Simple To This Multi-faceted. A RREQ is generated by node A and broadcasted to its neighbors. The RREQ propagates through the network until it reaches node C. Since node C has a route to node D it can comply with the RREQ and White, generate a RREP.
During the No Simple to this Multi-faceted propagation of the RREQ, a reverse path is set up to node A. The RREP is unicasted back to Essay, A. It uses the temporarily backward route set up by duncan in macbeth the RREQ. During the propagation of the reply, a forward route is set up to White Essay, node D by all intermediate nodes, resulting in the routing table shown in Table 20, thus all temporary routes are updated to active routes. Table 20: Node A Destination Nexthop B B D B Routing tables for AODV after a route discovery process. Node B Destination A C D Nexthop A C C Node C Destination B D A Nexthop B D B Node D Destination C Nexthop C After the route discovery process, only B and pricing, C have routes to White, all other nodes in the scenario. Node A does not know that there is a route to node C, nor does node D know of the route to A and B. Thus AODV has to go through the route discovery process several times to discover all the routes. This leads to more control traffic and higher delays.
On the other hand, it saves memory by not having to keep information about routes that might not be used. 60 DSR The ability to find routes differs slightly between the in macbeth DSR and Snow White, AODV protocol. DSR can make use of the source route carried in each packet header to discover routes to nodes by which the packet has traveled through. If new routes are found, DSR can take advantage of this without having to go through a new route discovery phase, thus reducing the number of on Poverty: Multi-faceted control packets and decreasing the delay. The memory usage of a node is instead increased by having to store more routes.
We consider the White same scenario as for the AODV protocol (Figure 26). Duncan. Node A needs a route to node D. Snow White. No data has been sent earlier, thus DSR has no knowledge of any routes. Essays. Since no routes are known, the RREQ propagates until it reaches node D. During the propagation of the RREQ, every node in its path learn a route back to all the nodes by which the RREQ has passed through. The RREP is Snow White unicasted back to relations, A, using the routes learned during the propagation of the RREQ. As the RREP propagates, each node also learns the Snow routes to reflective, all nodes for Snow White which the RREP has passed through, resulting in duncan the routing tables shown in Table 21. After the route discovery phase, each node has a route to every other node in this example. Snow Essay. Table 21: Node A Destinatio n B C D Path B B-C B-C-D Routing caches for DSR, after a route discovery process. New Product. Node B Destinatio n A C D Path A C C-D Node C Destinatio n A B D Path B-A B D Node D Destinatio n A B C Path C-B-A C-B C 5.7.2 Temporary backward routes When a RREQ propagates in search for a route in AODV, a temporary backward route is set up towards the requesting node.
A RREP might use this backward route. This route is normally set to expire after 3 seconds if it is Snow Essay not used. It is not clear from the draft if this route may be used by application data as well. Using this route for data affects the behavior of the protocol in some way and it is not described how the protocol should handle this. One of the problems with this temporary route is with the way it is set up. When the african american relations RREQ propagates, we do not know who will be using the backward route, so no active neighbors can be put into the active neighbor list. If during this time, a link failure or an expired route entry somewhere breaks the route, the rest of the nodes in the route are not informed of this and White Essay, therefore have redundant routes in their tables.
When the route is used again, the inductive and deductive research application data will come to a node in the route that does not have a valid entry for the destination and will therefore be dropped while a triggered RREP tries to inform the nodes in the route that it is broken. This problem will become more apparent in a network with a higher load. Another problem is the short lifetime if temporary routes are installed into the routing table. Lets say node A sets up a temporary route to D. White. Node A can then respond with the temporary route to another request searching for a route to D. Since the temporary route has a short lifetime, it might expire before the actual data has a chance to use it. This results in unnecessary control overhead and packet drops. To deal with this, the routing agent could chose to only allow RREP to and native, use the temporary route. Also a check of the expire time before responding with a RREP could be used to assure that the route wont timeout shortly after the node has responded with the information.
A question about this was directed to the author of the Snow Essay protocol with the in macbeth response that this check should not be done, instead the protocol should rely on the sequence numbers to Snow Essay, provide the freshness of a route. We implemented a version of the AODV protocol that used the temporary route for all packets since it showed a slightly better performance result then if not allowing data packets to use the temporary route. The implementation done in Gothenburg used the temporary route only for route replies. So we have a small difference in our implementations. 61 5.7.3 Buffers The use of send buffers in the routing protocol also affects the performance of the routing protocol; especially the size of the buffers and the time a packet is allowed to stay there before it is dropped. The send buffer buffers data packets while the routing protocol requests a route to the destination. Waste Problem. In our simulations, AODV used a buffer capable of holding 64 packets and allowing them to Snow, stay in the buffer for maximum 8 seconds. Allowing the packets to stay in the buffer for why is waste disposal materials a serious longer period of times will of Snow course increase the amount of successfully routed packets, but also increase the average delay. In Macbeth. Also the Snow Essay choice of queuing discipline will affect the Essay on Poverty: Solution to this Multi-faceted Problem measured performance.
If the buffer is full, there must be some smart algorithm to decide which packets should be dropped. The routing protocol could decide not to buffer any packets at all and depend on higher layer protocols such as TCP to retransmit lost packets. This would however affect the measured performance in Snow White the simulations and give unfair results for the protocol. 5.8 Discussion If we compare the work that we have done against the work that was done by the CMU Monarch project , many similarities can be seen. Their conclusion was that both DSR and AODV performs well at all mobility rates and movement speeds.
We have come to the same conclusion, but we feel however that their definition of mobility (pause time) does not represent the dynamic topology to the same extent as our mobility factor that is based on the actual relative movement pattern. The only node speeds that they have tested are 1 m/s and why is disposal, 20 m/s, which are not showing the complete range. Snow White. Our mobility factor has a speed range from 0 m/s up to 20 m/s and why is waste disposal of nuclear, shows how the Snow Essay protocols behave in the complete range. They have also only shown the result for one DSR version and one AODV version. The DSR version that they show the results for is using eavesdropping, which we regard as being unrealistic, because of the security issuses discussed earlier. The AODV version that they have used is not using hello messages, which changes the new product pricing behavior of AODV. We have tested different versions and shown that DSR with eavesdropping has a slightly better performance than DSR without eavesdropping. We have also shown that AODV with MAC-layer support and hello messages has better performance than AODV with only Snow White, MAC-layer support. Why Is A Serious. Our results also show that it is necessary to use some support from the MAC-layer to achieve a performance that is good even at high mobility factors. Snow White Essay. The CMU Monarch project, have used the number of sources as a definition of the load that is offered the and native american network. White. Their simulations with the strategies different number of sources are almost identical to each other.
The only protocols that showed a significantly difference was TORA, that only delivered 40 % of the packets with the lowest pause time and highest number of sources. Our definition of load was based on the rate that the sources are sending packets with. White. Even DSR that had the best results in the CMU paper fails to deliver a large fraction of the packets when the rate is increased. The increase of the rate also very clearly shows how much the overhead for pricing DSR increases compared to for instance AODV. 5.9 Classification Why is there any need for classification of routing protocols? If one routing protocol is superior than the Essay other routing protocols for instance in Essay on Poverty: No Simple Solution Multi-faceted very high mobile environments, why not always use that routing protocol? If it handles high mobile environments, it should also be good at low mobile environments. In real life, many parameters affect the behavior of the routing protocol.
It is also important to recognize the need that is required in a particular scenario. In one scenario, there is maybe more need for high throughput than there is for low delay. Snow. In another scenario there is maybe more need for low delay etc. This is becoming more and No Simple Solution, more important now, in particular when active networks  is becoming an interesting issue in networking. Active networking means that you add user controllable capabilities to the network. White. The network is in macbeth no longer viewed a passive mover of bits, but rather as a more general computation engine. This makes it possible for instance to adjust the routing protocol depending on White the scenario. You could basically send the inductive and deductive research routing protocol and let it install itself into Snow White Essay the nodes. 62 5.9.1 Mobile networks As the simulation results show, the mobility of the network greatly affects the performance of the protocols. It is crucial that the protocol ability to detect broken routes is fast enough and that they also react to reflective, these changes.
DSDV Since DSDV is dependent of White its periodic updates, its ability to deal with a dynamic topology is very poor. It has a poor ability to fast detect broken links and takes time to converge. This protocol should really be avoided for use in ad-hoc networks where it is crucial to duncan in macbeth, deal with frequent changing topology. Essay. This protocol could however be an option for inductive and deductive research networks that are static during long periods of times. Snow. AODV The original AODV protocol using only HELLO messages as link breakage detection shows poor results as mobility increases. This protocol needs better link breakage detection. Using lower layers such as MAC to why is, detect transmission errors can achieve this. If this is used, the Snow Essay protocol actually shows a very good performance. Essay On Poverty: No Simple Solution. This protocol is a definite choice for Snow White highly mobile networks. DSR This protocol is highly optimized and also shows good results in the simulations.
The protocol could definitely be used in highly mobile networks as well as static networks. 5.9.2 Size of networks When talking about the size of a network, it is strategies not only the number of nodes in the network that is of interest. The area that the nodes are spread out over is also interesting. This basically decides the connectivity of the network. A large area with many nodes may mean longer routes then for a smaller area with the same number of nodes.
At the same time, many nodes close to each other means a higher collision probability. DSDV This protocol does not scale well. Its use of periodic broadcasts limits the protocol to small networks. If the protocol would be used in Snow Essay large networks, the converge time to a steady state would increase when routes go up and down. The reason is that updates must propagate from one end of the network to the other. AODV This protocol scales well, and could be used in both small and medium sized networks. Duncan. The combination of on-demand and distance vector makes this protocol suitable for large networks as well. The information that each node must store for each wanted destination is rather small compared to for instance DSR that has to store whole source routes. In large networks however, the propagation of requests to all nodes is Snow a waste of resources. Inductive Research. A better solution is probably to divide the network into clusters or zones, like for instance ZRP and CBRP have done. Snow White. DSR This protocol has some limitations when it comes to new product, the size of the network.
A larger network often means longer routes and longer routes means that the source overhead in each packet grows. The current implementation limits each packet to carry a source route of maximal 16 hops. This can of course be adjusted, but one should keep in Essay mind the large overhead this causes. Essay On Poverty: No Simple Solution To This. One could imagine a network with 20 nodes connected in a straight line. Then this implementation would not manage to Snow White, route to all nodes. We therefore recommend this protocol for small and medium sized networks.
63 5.9.3 Network scenarios Conference For low mobility scenarios, like the conference scenario that we did simulations on, DSR is the best protocol to use if the hopcount is small (fewer than 5 hops). The reasons are high delivery rate, low delay and low message overhead in on Poverty: No Simple to this Problem terms of packets and byte overhead. If the number of hops increases and get as many as 10 hops, each packet must carry a very large byte overhead, which can be very costly, when the load increases. Essay. Another good candidate for this scenario when the number of hopcount increases is and deductive research one of the Snow AODV versions that use MAC-layer support. AODV has also a very high delivery ratio, but the number of duncan control packets is somewhat larger.
Event coverage In average mobile scenarios, like the Essay event coverage scenario, where nodes tends to cluster and almost all communication is within the clusters, DSR is by duncan all means the best protocol. White Essay. It has a very large delivery ratio and the overhead is very small, even counted in Essay on Poverty: Solution to this Problem bytes, because of the few hops required to reach the destination. White Essay. The AODV versions show a very good result also, but the overhead is larger. Solution Problem. So for these type sort of networks DSR it the best protocol. Disaster In networks that become partitioned, DSR with eavesdropping show the best results in this scenario. It has a high delivery ratio, high throughput, a delay around 1.2 seconds and low packet overhead.
It also uses only 5 hops in average to reach a destination. This protocol is therefore recommended in Snow White this type of scenario. Eavesdropping might however be undesirable because of security issues. Disposal Materials A Serious Problem. One other candidate for this scenario is AODV with MAC support. It has almost as high delivery ratio as DSR and also a lower delay. The packet overhead is twice as high but the byte overhead is smaller. 5.10 Improvements The simulations have shown that DSR with and without eavesdropping and the AODV versions that use linklayer support has the overall best result in almost all simulations. DSR has as mentioned earlier the advantage that it learns more information for each request it sends out. If a request goes from Snow S to D and the reply from D to duncan in macbeth, S, S will learn the Snow Essay route to all intermediate routes between S and D. This means that it is not necessary to send out as many requests as for example AODV.
The source routing approach is and deductive therefore very good in the route discovery and Snow, route maintenance cases. However, source routing is not desirable to use for data packets. First of in macbeth all, it adds a lot of overhead. Secondly it is White not as traditional as for instance distance vector or link-state that are widely used in wired networks. Strategies. Our proposal is Essay therefore to implement a protocol that is a combination of source routing and distance vector. Source routing should be used in and native american relations route discovery and Snow White Essay, route maintenance phases. Personal. These phases would also include that the routing tables where set up accordingly during the Snow White Essay propagation of the requests and replies. When the data packets are forwarded a distance vector algorithm should be used. The packets are simply forwarded to the nexthop according to new product strategies, the routing table. White. This in combination with that the and native american protocol stores several routes for each destination would probably mean a protocol with a performance that is even better than the White Essay protocols that have been simulated in duncan this master thesis.
64 6 Implementation study The implementation study that was conducted at Ericsson Mobile Data Design in Gothenburg  has implemented the AODV protocol. The goal was to deliver a working routing protocol as specified in the original AODV draft . 6.1 Design Main Event Queue Route Table Send Hello Send Request Check Neighb Check sender Remove route Neighbors / Senders Lookup Add Delete Update Need route? Add Delete Update time Is member? Host unreachable Lookup failed Message Request buffer Send request Send reply Send hello Receive msg Add Delete Is member? Rreq Rrep Hello Route add Route del User space /dev/route Iotcl() Icmp.c UDP FIB Kernel Table Kernel route.c Other daemons Figure 27: Overview of AODV daemon. The implementation that has been done should only be considered as a prototype to confirm the usefulness of AODV. It is implemented as a daemon in user space. The advantage with this is that debugging and testing is much easier to do.
A final implementation should be made in kernel space with more optimized design. Snow. Thus abandon the research modular design and optimize the Essay code to essays, go really fast. Figure 27 shows the Snow design of the user space daemon and how it interacts with the kernel code. Personal Reflective. The different modules will be explained in the following chapters. 6.1.1 Main Main ties together all other modules of the user space daemon. It is also in main that the AODV specific code lies. 65 6.1.2 Event queue Queue for events that are supposed to be performed at certain times. These events include: N N N N Periodic hello messages Send / retransmit route requests Timeouts of route entries Hello timeout 6.1.3 Route table This module is an interface against the submodules Daemon Table and Snow, Kernel Table. Research. It takes care of these two, so when you want to lookup or change a route from Main, you only have to Snow White, do one call to this module instead of duncan two to the both submodules.
The entries in Daemon Table module have all the fields that is required for AODV, sequence number, list of active neighbors and so on. The operations supported are Lookup, Add and Delete. The Kernel Table is Snow Essay not a table in the sense Daemon Table is, instead this submodule just communicates with the kernel, sending messages about adding and essays, deleting entries and receives netlink need-route messages. Snow. 6.1.4 Neighbors / senders Keeps track of the neighbors of a node. A neighbor is a host that sends/receives hello messages that is duncan in macbeth directly received/sent by another node. This demands that the links are bi-directional. Snow White Essay. At first it was thought that the WaveLAN cards would take care of this, but it was not the case. Duncan In Macbeth. The signal strength and the range was different between the White Essay hosts. To be able to guarantee bi-directional link, the inductive concept Sender was added. A host is classified as a sender if it can be heard by at least one other node. When sending hello messages a node sends the White Essay list of current Senders and inductive and deductive research, if the Snow White Essay receiver of the Hello messages is in this list, it is a Neighbor and can start act as one 6.1.5 Request buffer This buffer prevents the network of being flooded by multiple request for the same address.
This buffer stores already processed requests. Duncan In Macbeth. 6.1.6 Message Handles the different types of messages that the Essay daemon can send and receive. These messages are: N N N Hello Route Request Route Reply. 6.2 Setup The computers used for Essay Problem this implementation study was: N N 2 stationary computers with Lucent WaveLAN ISA cards. 3 laptops with Lucent WaveLAN PCMCIA cards.
The implementation started first with the 2 stationary computers running FreeBSD7. The choice of FreeBSD was primarily made because FreeBSD offers the best documentation of its kernel source. It was later discovered when the laptops arrived that FreeBSD was incompatible with the Lucent WaveLAN PCMIA cards in Snow Essay the laptops. Linux8 however has support for Essay No Simple Solution to this Multi-faceted Problem both variants of the LucentWaveLAN cards and Linux was therefore chosen as development operating system. It is not very hard to port the code to FreeBSD in the future if so desired. 7 8 FreeBSD 2.2.6 Linux Red Hat 5.1 66 6.3 Testing The purpose of Snow testing the inductive and deductive research implementation is to verify that the implementation works correctly and to White, see if the performance is suitable for reflective essays real life applications. 6.3.1 Correctness To verify that the implementation of AODV behaved correctly, computers were placed in White different scenarios to test the different parts of the protocol. The following tests where made: N N N N N N N Bi-directional links and personal reflective, neighbors: Tests that two nodes can send hello messages to each other and registry the counterpart as a neighbor. Unidirectional links and neighbors: It tests the same as above, but with the difference that we only Snow White, have an uni-directional link, so only one of the nodes can hear the other and registry him as a neighbor. Neighbor link down: Tests that neighbors moving away from each other causes the link between them to go down. Zero hop route requests: Tests that a request to a neighbor that also is the in macbeth requested destination generates a reply that is correctly received.
This is not the normal operation of the protocol, but could happen if two nodes are in Snow Essay range but have not accepted each other as neighbors. Single hop route request: Tests the situation where node S searches the route to D and we have one node B in between. S broadcasts a request that is caught by in macbeth B, which knows the route to Essay, D and sends a reply back to S. Multihop route request: Almost the and deductive research same situation as the Snow White single hop route request. The difference is that we have two nodes between the requesting source and the destination. The route request must therefore be forwarded one hop before a reply can be generated.
Triggered route reply: Tests that the reflective essays triggered route reply is Essay generated whenever a route goes down. Duncan In Macbeth. 6.3.2 Performance No actual performance tests were done. The results for so few nodes would be misleading. Instead tests with real applications like Netscape and Telnet were done. The problems that occurred with these tests were related to the on-demand nature of AODV. Snow. Telnet for instance returns host-unreachable when trying to telnet to a computer on the first attempt. The second attempt however is successful. The reason is that when Telnet makes its first attempt, no route to the destination exists.
This will result in an error message from the kernel to Essay No Simple Solution Multi-faceted Problem, Telnet, at the same time as a new request is Snow White Essay sent to the neighbors. This request will eventually find a route to the destination and it is installed in the routing table. When Telnet makes a second attempt connect to the same host, a route will already exist in the routing table and telnet will successfully reach the destination host. The solution to this problem is simply to research, take care of the error messages that the kernel sends to the application. The error message should be buffered and if a route is not found in a certain amount of time, the error message should be sent to the application, but if a route is actually found the Snow White Essay error message can be discarded. 6.4 Problems / Limitations Problems that occurred during the implementation include: N N N FreeBSD incompatibilities: As mentioned before, lack of functional drivers to FreeBSD forced the implementation study to be done under Linux. Address: The current prototype requires that each node participating in why is waste disposal materials a serious problem the network have a predefined unique IP-address. White Essay. There is a great need for a dynamic assigned IP-address architecture, which assigns nodes IP-addresses as they enter the Essay on Poverty: No Simple to this Problem network. IPv6 holds such functionality. Essay. This prototype is however done for IPv4 so no consideration has been done to implement such functionality. Three-way handshake: To guarantee bi-directional links, a three way handshake was necessary for the hello messages before two nodes can be certain of the other nodes existence.
The handshake uses piggybacking. It concatenates a list of all nodes it receives hello messages from to personal reflective essays, the hello messages it sends. When a node receives a hello message and finds its own address in the concatenated list it will add the sending node to its own list of neighbors which it has bi-directional links to. Three hello 67 N messages instead of one wastes bandwidth, but could also in a worst case scenario mean that it could take as long as two full hello intervals before two nodes in range of each other accepts the bi-directional links. Temporary routes: When a request is broadcasted from a node, it will propagate through the Snow network and at inductive, the same time install a temporary route back to the source.
The problem with this temporary route is first of all that the request is unaware of Essay if the waste of nuclear problem route ever will be used and secondly who will use it. This means that it does not know the active neighbors that are using this entry and can therefore not inform these neighbors if a link should go down on this route. Snow Essay. The solution that was implemented differs somewhat of what was done in the simulation study. The solution is to store the temporary routes separately and only install them in the routing table when the african american route reply is propagating back through the network. 6.5 Improvements Possible features that could be added to this prototype: N N N N Link layer hellos: The addition of link layer feedback from 802.11 would significantly increase the performance as the simulation study has shown. Essay. Redundant routes: Store all routes to a destination, not only the pricing strategies one we are currently using. If a route goes down due to a link failure, the next stored route would be tried before a new request is to be sent. This saves a lot of overhead a and makes the delay somewhat smaller. Dynamic IP-addresses: As mention under limitations, dynamic address assignment is a requirement for White Essay these kind of networks.
Multicast: Multicast groups within a ad-hoc network could be added. The latest AODV draft has support for this. 6.6 Implementation conclusions The implementation of the AODV protocol has shown that it is possible to in macbeth, get these protocols to work in real-life. Snow. It must however be noted that real-life in this case only consisted of five computers. The AODV prototype has also given some insight into the problems that arise when trying to in macbeth, run real applications on an ad-hoc network. White Essay. Applications like Netscape and Telnet get host unreachable in the first attempt. The second attempt finds the personal reflective route successfully. This has to do with the on-demand feature of the AODV protocol.
68 7 Conclusions 7.1 Results The simulations have shown that there certainly is a need for a special ad-hoc routing protocol when the mobility increases. Essay. It is however necessary to have some sort of feedback from the link-layer protocol like IEEE MAC 802.11 when links go up and down or for neighbor discovery. To only inductive research, be dependent on periodic messages at Snow White Essay, the IP-level will result in a very high degree of packet losses even when mobility increases a little. Duncan. The simulations have also shown that more conventional types of protocols like DSDV have a drastic decrease in Snow White performance when mobility increases and are therefore not suitable for mobile ad-hoc networks. Research. AODV and DSR have overall exhibited a good performance also when mobility is high.
DSR is however based on source routing, which means that the byte overhead in each packet can affect the total byte overhead in the network quite drastically when the offered load to the network and White, the size of the network increases. In these situations, a hop-by-hop based routing protocol like AODV is more desirable. One advantage with the source routing approach is however that in its route discovery operation it learns more routes. Source routing is however not desirable in ordinary forwarding of data packets because of the inductive research large byte overhead. A combination of AODV and DSR could therefore be a solution with even better performance than AODV and Snow Essay, DSR. Another key aspect when evaluating these protocols is to duncan in macbeth, test them in realistic scenarios. Snow Essay. We have tested them in three types of scenarios. DSR had the best performance, but the large byte overhead caused by duncan in macbeth the source route in each packet makes AODV a good alternate candidate.
It has almost as good performance. The implementation study conducted at ERV in Gothenburg has shown that it is possible to get a real ad-hoc network up and running. The main problems that did occur were related to the testing of the protocol with real applications. When a route was needed by the application and the route did not exist in the routing table, the kernel informed the applications of a connection error before giving the routing protocol enough time to find a route. 7.2 Further studies Ad-hoc networking is White Essay a rather hot concept in computer communications.
This means that there is much research going on and many issues that remains to be solved. African And Native. Due to limited time, we have only focused on the routing protocols. However there are many issues that could be subject to White Essay, further studies. First of No Simple to this all, the simulator environment could be improved. These are just some of the Essay improvements that could be made: N N More routing protocols, for personal reflective instance TORA, ZRP and CBRP. Measurement of Snow White computing complexity.
Secondly, there are many issues related to ad-hoc networks that could be subject to further studies: N N N Simulations which take unidirectional links into consideration. Some sort of analysis of whether many small control messages are more costly to send in terms of resources than fewer large control messages. Security: A very important issue that has to be considered is the security in duncan in macbeth an ad-hoc network. Routing protocols are prime targets for Snow White Essay impersonation attacks. Because ad-hoc networks are formed without centralized control, security must be handled in in macbeth a distributed fashion.
This will probably mean that IP- 69 N N N N N N Sec  authentication headers will be deployed, as well as the necessary key management to distribute keys to the members of the ad-hoc network. Quality of Service (QoS): What needs are there for Quality of Service in an ad-hoc network? This is related to what the networks actually will be used for. Hand-over of real-time traffic between nodes. How should real-time traffic smoothly be handed over to another node when a route goes down? Should flooding be used before a route is Snow White Essay found? Multicast: We have only looked at unicast routing. Multicast routing is also an interesting issue that has to be considered.
Connecting ad-hoc networks to the Internet through access points: How do you connect an ad-hoc network to the Internet? It is not possible to why is disposal of nuclear problem, just add the access point as default in the routing tables. This would mean that nodes without a route to Essay, a certain destination would be routed to the Internet. Mobile IP: Integration of mobile IP into ad-hoc networks. Addressing of why is waste disposal materials a serious hosts: How should the hosts in an ad-hoc network be addressed? What happens if one adhoc network is partitioned in to Snow White, two separate networks or two ad-hoc networks are merged into and native relations one new larger ad-hoc network? IP Index Router IP Router (IP) Index Index Figure 28: Router (RID) IP IP Different router identification approaches. From left to right: 3a, 3b, 3c. There are basically three types of identifiers to consider (Figure 28): 1) Interface identifiers: Interfaces are present on both routers and Snow White, hosts.
In the pricing Internet addressing architecture, interfaces are identified by IP addresses. 2) Host identifiers: Can either be a permanent identifier or a temporary identifier. Snow. 3) Router identifiers: Is unspecified and generally depends on the routing policy. There are three approaches to MANET router identification and addressing currently being considered: a) Single IP address (AODV): Identifies a MANET node (both the router and the host) with a single IP address. This approach leaves several issues open: N How to support sets or subnets of duncan in macbeth hosts attached to a MANET router?
N How to support the use of multiple wireless interfaces? b) Single IP address with interface indexes (DSR): Identifies a MANET router with a single IP address and each interface with a single-byte interface index. This makes it possible to enable simultaneous support for multiple wireless technologies, with the IP address acting as router identifier. The problem with this scheme is that it is not IP in the classical sense where interfaces are identified by IP addresses. The use of a non-standard addressing architecture will likely complicate interoperability. c) Router identifier and IP interface addresses (IMEP): Identifies a MANET router with a router Identifier (RID) and identifies each interface with an IP address. This approach can support sets or subsets of attached hosts and simultaneous use of multiple wireless technologies.
Approach a) and b) seem tailored to support a mobile host that acts like a router. Essay. Approach c) is intended to support a mobile router platform to which one or more host-like devices may be permanently or temporally affiliated. Duncan. These approaches say nothing about how IP addresses are assigned to interfaces (on hosts or routers), or what the RID is and how it is assigned. This is a separate problem, although one which is related to routing. 70 8 References  Dimitri Bertsekas and Robert Gallager, “Data Networks - 2nd ed”. Prentice Hall, New Jersey, ISBN 013-200916-1. Snow White Essay.  Bommaiah, McAuley and reflective, Talpade. AMRoute, “Adhoc Multicast Routing Protocol”, Internet draft, drafttalpade-manet-amroute-00.txt, August 1998. Work in progress. White.  Josh Broch, David A. In Macbeth. Maltz, David B. Johnson, Yih-Chun Hu and Snow White, Jorjeta Jetcheva, “A performance Comparison of Multi-hop Wireless Ad Hoc Network Routing Protocols”. Mobicom'98, Dallas Texas, 25–30 October, 1998.  Josh Broch, David B. Essay No Simple Problem. Johnsson, David A. Maltz, “The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks”. Snow White. Internet Draft, draft-ietf-manet-dsr-00.txt, March 1998. Work in progress.  Scott Corson and Joseph Macker, “ Mobile Ad Hoc Networking (MANET): Routing Protocol Performance Issues and Evaluation Considerations”.
Internet-Draft, draft-ietf-manet-issues-01.txt, March 1998. Work in progress.  M.Scott Corson, S. Papademetriou, Philip Papadopolous, Vincent D. Park and No Simple Solution to this Multi-faceted Problem, Amir Qayyum, “An Internet MANET Encapsulation Protocol (IMEP) Specification”. Internet draft, draft-ietf-manet-imepspec01.txt, August 1998. Work in progress.  Kevin Fall and Kannan Varadhan, “ns notes and documentation”. The VINT project, UC Berkeley, LBL, USC/ISI, and Xerox PARC, May 1998. Work in progress. Essay.  Zygmunt J. Haas and Marc R. Pearlman, “The Zone Routing Protocol (ZRP) for Ad Hoc Networks”, Internet draft, draft-ietf-manet-zone-zrp-01.txt, August 1998.
Work in progress.  IEEE Computer Society LAN MAN Standards Committee, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications”, IEEE Std 802.11-1997. The Institute of Electrical and Electronics Engineers, New York.  Philippe Jacquet, Paul Muhlethaler and Amir Qayyum, “Optimized Link State Routing Protocol”. Internet draft, draft-ietf-manet-olsr-00.txt, November 1998. Work in progress. Duncan In Macbeth.  Mingliang Jiang, Jinyang Li and Yong Chiang Tay, “Cluster Based Routing Protocol (CBRP) Functional specification”. Internet draft, draft-ietf-manet-cbrp-spec-00.txt, August 1998. White. Work in progress.  David B. Johnson and David A.Maltz, “Dynamic source routing in ad hoc wireless networks”. In Mobile Computing, edited by Tomasz Imielinski and Hank Korth, chapter 5, pages 153-181. Kluwer Academic Publishers.  David B. Johnson and David A. Maltz, “Protocols for pricing adaptive wireless and mobile computing”. In IEEE Personal Communications, 3(1), February 1996.  Stephen Kent and Randall Atkinson, “Security Architecture for the Internet Protocol”, Internet draft, draft-ietf-ipsec-arch-sec-07.txt, July 1998.
Work in progress. White.  Mobile Ad-hoc Networks (MANET). URL: http://www.ietf.org/html.charters/manet-charter.html. (1998-11-29). Work in progress. 71  Vincent D. Park and research, M. Scott Corson, “Temporally-Ordered Routing Algorithm (TORA) Version 1: Functional specification”. Snow. Internet draft, draft-ietf-manet-tora-spec-01.txt, August 1998. Work in progress.  Vincent D. Park and M. Scott Corson, “A performance comparison of the Temporally-Ordered Routing Algorithm and Ideal Link-state routing”. In Proceedings of IEEE Symposium on Computers and Communication ’98, June 1998.  Charles E. Perkins, “Mobility support, Mobile IP and Wireless Channel Support for ns-2”, presentation slides. URL: http://www.svrloc.org/ charliep/mobins2/, (1998-11-29). Work in progress.  Charles E. Perkins, “Ad Hoc On Demand Distance Vector (AODV) Routing”. Essay On Poverty: No Simple. Internet draft, draft-ietfmanet-aodv-01.txt, August 1998.
Work in progress.  Charles E. Snow White Essay. Perkins, “Ad Hoc On Demand Distance Vector (AODV) Routing”. Internet draft, draft-ietfmanet-aodv-02.txt, November 1998. Work in progress.  Charles E. Perkins, “Mobile Ad Hoc Networking Terminology”. Internet draft, draft-ietf-manet-term00.txt, October 1997. Work in progress.  Charles E. Perkins and duncan, Pravin Bhagwat, “Highly dynamic Destination-Sequenced Distance-Vector routing (DSDV) for mobile computers”. In Proceedings of the Snow Essay SIGCOM '94 Conference on waste disposal Communications Architecture, protocols and Applications, pages234-244, August 1994. A revised version of the paper is available from http://www.cs.umd.edu/projects/mcml/papers/Sigcomm94.ps. (1998-11-29)  Larry L. Snow. Peterson and Essay on Poverty: Solution to this Multi-faceted Problem, Bruce S. Snow. Davie, “Computer Networks - A Systems Approach”. Essay No Simple Solution Multi-faceted. San Francisco, Morgan Kaufmann Publishers Inc. ISBN 1-55860-368-9.  Plummer, D., An Ethernet Address Resolution Protocol - or - Converting Network Protocol Addresses to Snow Essay, 48.bit Ethernet Address for Transmission on Ethernet Hardware, RFC-826, MIT, November 1982.  Theodore S. Rappaport, “Wireless Communications: Principles and african relations, Practice”. New Jersey, Prentice Hall. ISBN 0-13-375536-3.  Raghupathy Sivakumar, Prasun Sinha and Vaduvur Bharghavan, “Core Extraction Distributed Ad hoc Routing (CEDAR) Specification”, Internet draft, draft-ietf-manet-cedar-spec-00.txt, October 1998.
Work in progress.  Martha Steenstrup, “Routing in communication networks”. New Jersey, Prentice Hall. Snow White Essay. ISBN 0-13010752-2.  Jerry Svedlund and Johan Kopman, “Routing protocols in wireless ad-hoc networks - An implementation study”. African And Native American. Uppsala: Uppsala University. Master thesis. White.  D. L. Waste Disposal Materials. Tennenhouse and D. Wetherall, “Towards an Snow Essay, active network architecture”. In Multimedia Computing and Networking 96, San Jose, CA, Jan 1996.  The CMU Monarch Project. “The CMU Monarch Projects Wireless and waste materials a serious problem, Mobility Extensions to ns”. URL: http://www.monarch.cs.cmu.edu/. (1998-11-29).
Work in White Essay progress. 72 Appendix A -Terminology This appendix contains some terminology  that is related to ad-hoc networks. A.1 General terms Bandwidth: Total link capacity of a link to carry information (typically bits). Channel: The physical medium is divided into logical channel, allowing possibly shared uses of the why is waste problem medium. Channels may be made available by subdividing the medium into distinct time slots, distinct spectral bands, or decorrelated coding sequences. Convergence: The process of approaching a state of equilibrium in which all nodes in the network agree on a consistent state about the topology of the network.
Flooding: The process of delivering data or control messages to every node within the any data network. Host: Any node that is not a router. Interface: A nodes attachment to a link. Link: A communication facility or medium over which nodes can communicate at the link layer. Loop free: A path taken by a packet never transits the same intermediate node twice before arrival at the destination. MAC-layer address: An address (sometimes called the link address) associated with the Essay link interface of a node on a physical link. Next hop: A neighbor, which has been designated to forward packets along the duncan in macbeth way to a particular destination. Snow White. Neighbor: A node that is within transmitter range from and deductive another node on the same channel. Node: A device that implements IP.
Node ID: Unique identifier that identifies a particular node. Router: A node that forwards IP packets not explicitly addressed to itself. In case of Snow White Essay ad-hoc networks, all nodes are at least unicast routers. Routing table: The table where the materials problem routing protocols keep routing information for Snow White Essay various destinations. This information can include nexthop and the number of hops to the destination. Scalability: A protocol is personal scalable if it is applicable to large as well as small populations. Source route: A route from the source to White, the destination made available by the source. Throughput: The amount of data from a source to a destination processed by the protocol for which throughput is to be measured for instance, IP, TCP, or the new product MAC protocol. 73 A.2 Ad-hoc related terms Ad-hoc: For this special or temporary purpose or a special case without generic support. AODV: Ad-Hoc On-Demand Distance Vector.
Routing protocol for wireless ad-hoc networks. Asymmetric: A link with transmission characteristics that are different of the transmitter and White Essay, receiver. For instance, the african and native range of one transmitter may be much higher than the range of Snow Essay another transmitter on the same medium. The transmission between the two hosts will therefore not work equally well in in macbeth both directions. See also symmetric. Beacon: Control message issued by a node informing other nodes in Essay its neighborhood of its continuing presence. Bi-directional: see symmetric. CBRP: Cluster Based Routing Protocol. Routing protocol for wireless ad-hoc networks.
Cluster: A group of nodes typically in range of each other, where one of the nodes is elected as the in macbeth cluster head. The cluster head ID identifies the cluster. Each node in the network knows its corresponding cluster head(s) and therefore knows which cluster(s) it belongs to. Essay. DSDV: Dynamic Sequenced Distance Vector. Routing protocol for wireless Ad Hoc networks. In Macbeth. DSR: Dynamic Source Routing. Routing protocol for wireless Ad Hoc networks. Proactive: Tries to maintain the routing map for White the whole network all the time.
See also reactive. Reactive: Calculates route only upon receiving a specific request. See also proactive RREQ: Routing Request. A message used by duncan in macbeth AODV for the purpose of discovering new routes to a destination node. RREP: Route Reply. A message used by AODV to reply to route requests. Symmetric: Transmission between two hosts works equally well in both directions.
See also asymmetric. TORA: Temporally Ordered Routing Algorithm. Routing protocol for wireless ad-hoc networks. White Essay. Unidirectional: see asymmetric. ZRP: Zone Routing Protocol. Routing protocol for wireless ad-hoc networks. 74 Appendix B - AODV implementation for in macbeth ns This appendix contains a little more details about the implementation of AODV that we did for ns. The implementation of AODV is Snow done according to african and native american, the draft  released in August 1998. B.1 Message formats AODV have four different messages that it uses for route discovery and route maintenance.
All messages are sent using UDP. B.1.1 Route Request – RREQ The format of the route request message is shown in Essay Figure 29. Duncan In Macbeth. 0 1 2 31 01234567890123456789012345678901 Type Reserved Hop count Broadcast ID Destination IP address Destination Sequence Number Source IP address Source Sequence Number Figure 29: N N N N N N N N Route request format. Snow. Type: Type of essays message. Reserved: Reserved for future use. Currently sent as 0 and Snow, ignored on reception. Hop count: Number of hops from the source IP address to and native american relations, the node handling the request. Snow White Essay. Broadcast ID: A sequence number identifying the personal essays particular request uniquely when taken in conjunction with the Essay source nodes IP address.
Destination IP address: IP address of the destination for which a route is required. Destination sequence number: The last sequence number received in the past by the source for any route towards the destination. Source IP address: IP address of the node that originated the request. Source sequence number: Current sequence number for route information generated by duncan the source of the route request. 75 B.1.2 Route Reply - RREP The format of the route reply message is shown in White Essay Figure 30. 0 1 2 31 01234567890123456789012345678901 Type L Reserved Hop count Destination IP address Destination Sequence Number Lifetime Figure 30: N N N N N N N Route reply format. Type: Type of message. L: If the L-bit is Essay on Poverty: Solution to this Problem set the White Essay message is a hello message and contains a list of the nodes neighbors. Reserved: Reserved for future use. Currently sent as 0 and ignored on inductive research reception. Hop count: Number of hops from the source IP address to the destination IP address.
Destination IP address: IP address of the Essay destination for new product which a route is supplied. Snow Essay. Destination sequence number: The destination sequence number associated to the route. Lifetime: Time for which nodes receiving the Reply consider the route to be valid. B.1.3 Hello Hello messages are a special case of Route reply messages. Essay On Poverty: No Simple To This Multi-faceted Problem. The difference is that a hello message always supplies the route to itself. Essay. This means that the new product pricing hop count field is set to Snow White, 0, the personal essays destination address set to Snow, the nodes IP address and the destination sequence number set to the nodes latest sequence number.
B.1.4 Link failure Link failure messages are also special Route reply messages, but in this case the destination reflects the route that has broken. The broken route is assigned an infinite hop count and on Poverty: No Simple Solution to this Problem, a sequence number that is increased with one. Snow. 76 B.2 Design Figure 31 shows how AODV was designed when implemented for ns. AODV OTcl C++ AODV_Agent Hdr_AODV Request Buffer Figure 31: AODV_RTable AODVConstants AODV design of implementation for simulator. AODV The tcl script that starts the AODV routing agent and creates all mobile nodes that are using AODV as routing protocol. AODV_Agent Implements all AODV specific parts.
Handles RREQ, RREP, Hello and Triggered RREP. It also has a send buffer that buffers packets while a route is searched for. The timers that handles timeouts on personal reflective essays route entries and Snow, the send buffer are also implemented here. Duncan In Macbeth. Hdr_AODV Defines the Snow White message format for all messages that AODV uses. Personal Reflective Essays. Request Buffer Implements the request buffer that prevents a node to process the same RREQ multiple times. Snow White Essay. AODV_RTable The routing table that AODV uses. The routing table also implements the new product pricing active neighbor list for Snow each route entry. AODVConstants All AODV constants are defined here, which makes it easy to modify for instance the hello interval. 77 B.3 Important routines B.3.1 Sending RREQ RREQ will only be sent by why is waste of nuclear a serious the source nodes (no intermediate nodes sends RREQs), if there does not exist any route for Snow the destination. 1. 2. 3. Duncan In Macbeth. 4. 5. 6. 7. 8. 9. 10. White Essay. 11.
12. B.3.2 if ( no route exists ) else Receiving RREQ When a node receives a RREQ, it must first of Essay Solution to this all decide if it already has processed the RREQ. The RREQ is discarded if it has been processed. Otherwise the source address and Essay, the broadcast ID from RREQ will be buffered to prevent it from being processed again. 1. 2. Why Is Waste Disposal A Serious Problem. 3. 4. 5. if ( (source addr, broadcast ID) in Snow White request buffer ) else The next step is to create or update the route entry in the routing table. This route can be used by the RREP when a route is found.
1. 2. 3. 4. 5. 6. 7. 8. if ( no route to source addr ) elseif ( source seqno in essays RREQ source seqno in Snow Essay route entry ) elseif ((source seqno in RREQ = source seqno in route entry) AND ( hop count in No Simple Solution to this Multi-faceted Problem RREQ hop count in route entry )) Then, the White node must check if it knows the route to inductive and deductive research, the wanted destination. Snow White. If the and deductive research node knows the route it will unicast a RREP to the source. Otherwise it will forward the White RREQ. 1. Of Nuclear Materials Problem. 2. 3. Snow Essay. 4. 5. 6. 7. 8. 9. 10. if ( you are destination of personal reflective RREQ ) elseif (( have route to destination ) AND (destination seqno in route entry = destination seqno in RREQ)) else 78 B.3.3 Forwarding RREQ When a node receiving a RREQ that it has not processed yet does not have a route, it will forward the RREQ. 1. 2. 3. 4. Snow White. 5. create a RREQ packet: copy all fields from pricing strategies received RREQ into new packet increment hop count field locally broadcast new RREQ packet discard received RREQ B.3.4 Forwarding RREP When a node receives a RREP that is not addressed for the node, it will set up the forward route by updating the routing table and forward the RREP back to the requesting source. This part is White however not explicit specified in the AODV draft. 1. 2. Reflective Essays. 3. White. 4. 5. 6. 7. 8. 9. 10. 11. 12.
13. if ( route to requested destination does not exist ) elseif(destination seqno in Essay on Poverty: No Simple to this Problem RREP destination seqno in route entry) elseif ((destination seqno in RREP = destination seqno in route entry ) AND ( hop count in RREP hop count in entry )) if (route to requesting source exists) B.3.5 Receiving RREP When the originating source receives the White Essay RREP it will update the routing table. And Native American Relations. 1. 2. 3. 4. 5. 5. 6. 7. 8. 9. 10. 11. if (route to destination does not exist) elseif (destination seqno in RREP destination seqno in White Essay route entry) elseif (( destination seqno in RREP = destination seqno in route entry ) AND (hop count in RREP hop count in entry )) else 79 B.3.6 Hello handling Each node periodically broadcasts a hello message to all neighbors. When a node receives a hello message it knows that the sending node is a neighbor and will update the routing table. 1. 2. 3. 4. Essay Solution To This Problem. 5. 6. Snow. 7. 8. And Native American. 9. Snow. B.3.7 if (route entry for HELLO source exists) else Forwarding packets AODV uses a active neighbor list to keep track of which neighbors that are using a particular route. These lists are used when sending triggered route replies. The neighbor lists are updated every time a packet is forwarded. 1. 2. 3. In Macbeth. 4. 5. Snow Essay. 6. B.3.8 if (route entry to destination exists) Sending Triggered RREP Link breakages are detected by either the link layer which notifies the routing agent or by new product using hello messages. If a node has not received hello messages from a node for a certain amount of Essay time it will assume that the link is down. New Product Strategies. Every time a link is detected as down, AODV will send a Triggered RREP to inform the Snow White affected sources. 1. 2. Essay On Poverty: No Simple Problem. 3. 4. B.3.9 for (each address in White the active neighbor list for a route entry) Receiving Triggered RREP Every time a Triggered RREP is on Poverty: to this Problem received informing about a broken link, the Snow Essay affected route entry must be deleted and personal essays, neighbors using this entry must be informed.
1. 2. 3. 4. if (have active neighbors for broken route) delete route entry for broken route 80 Appendix C -Simulator screenshots This appendix shows some screenshots of Snow Essay Network animator and Ad-hockey. Network animator is the visualization tool for ns and duncan, Ad-hockey is the visualization for the mobility extension developed by Snow the CMU Monarch project. Duncan. C.1 Network animator Figure 32 shows a screenshot of Network animator. The scenario contains 19 nodes in White Essay a wired network. Personal Reflective Essays. Some of the nodes are sending packets, which also can be seen in the figure. White Essay. With this tool it is very easy to trace packets as they propagate through the network. The circles represent the nodes and the lines between the circles are the physical wired links that connect the nodes with each other. Figure 32: Screenshot – Network animator. 81 C.2 Ad-hockey The screenshots of Ad-hockey that can be seen in Figure 33, Figure 34 and Figure 35 shows the playback trace of the why is disposal of nuclear a serious realistic scenarios that with did simulations on.
The big white rectangle in the middle is the movement area. The different colored circles are the nodes. The colors of the nodes represent what action the nodes are performing at Essay, the moment. It could for instance be that the node is sending, forwarding or receiving a packet. The lines between the nodes do not represent wired links. The lines are actually packets that propagate from node to node. Strategies. The detached rectangles and Snow, lines that also can be seen within the movement area are obstacles. Figure 33: Screenshot – Ad-hockey – Conference scenario. 82 Figure 34: Screenshot – Ad-hockey – Event coverage scenario. Inductive And Deductive Research. Figure 35: Screenshot – Ad-hockey – Disaster area. 83 . TERM Spring #039;00 PROFESSOR Hesham TAGS Computer network, . routing protocol, ad-hoc network.
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07 Adhoc Networks. Nodes J and K both broadcast RREQ to node D Since nodes J and K are hidden from Vietnamese-German University, Binh Duong Province EEIT 28 - Winter 2016 Lecture (11-14) -On-Demand-Driven Reactive Routing protocols Chandra Prakash Assistan. Copyright © 2017. Course Hero, Inc. Privacy Terms.
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Introductions, Body Paragraphs, and Conclusions for an Argument Paper. The following sections outline the Essay generally accepted structure for an academic argument paper. Keep in mind that these are guidelines and that your structure needs to be flexible enough to meet the waste disposal a serious requirements of your purpose and audience. You may also use the following Purdue OWL resources to Snow White help you with your argument paper: The introduction is the broad beginning of the paper that answers three important questions: What is this? Why am I reading it? What do you want me to african do? You should answer these questions by doing the Snow Essay following: Set the context provide general information about the why is disposal of nuclear materials a serious problem main idea, explaining the situation so the reader can make sense of the topic and Essay the claims you make and support State why the main idea is reflective essays important tell the reader why he or she should care and keep reading. Your goal is to create a compelling, clear, and convincing essay people will want to read and Essay act upon State your thesis / claim compose a sentence or two stating the position you will support with logos (sound reasoning: induction, deduction), pathos (balanced emotional appeal), and ethos (author credibility).
For exploratory essays, your primary research question would replace your thesis statement so that the audience understands why you began your inquiry. An overview of the types of sources you explored might follow your research question. If your argument paper is long, you may want to forecast how you will support your thesis by outlining the structure of your paper, the sources you will consider, and the opposition to your position. You can forecast your paper in many different ways depending on the type of paper you are writing. Your forecast could read something like this:
First, I will define key terms for my argument, and new product pricing then I will provide some background of the situation. Next I will outline the White Essay important positions of the argument and explain why I support one of problem these positions. Lastly, I will consider opposing positions and discuss why these positions are outdated. I will conclude with some ideas for taking action and possible directions for future research. When writing a research paper, you may need to use a more formal, less personal tone. Snow White! Your forecast might read like this: This paper begins by providing key terms for the argument before providing background of the situation. Next, important positions are outlined and supported. To provide a more thorough explanation of these important positions, opposing positions are discussed. Solution To This Multi-faceted! The paper concludes with some ideas for Essay taking action and possible directions for future research.
Ask your instructor about what tone you should use when providing a forecast for your paper. These are very general examples, but by adding some details on your specific topic, a forecast will effectively outline the why is disposal of nuclear materials a serious structure of your paper so your readers can more easily follow your ideas. Your thesis is more than a general statement about Snow White, your main idea. It needs to african and native american establish a clear position you will support with balanced proofs (logos, pathos, ethos). Use the checklist below to help you create a thesis.
This section is adapted from Writing with a Thesis: A Rhetoric Reader by David Skwire and Sarah Skwire: Make sure you avoid the following when creating your thesis: A thesis is White not a title: Homes and schools (title) vs. Parents ought to participate more in the education of their children (good thesis). A thesis is not an personal essays announcement of the subject: My subject is the Essay incompetence of the Supreme Court vs. The Supreme Court made a mistake when it ruled in favor of George W. American Relations! Bush in the 2000 election. A thesis is not a statement of absolute fact: Jane Austen is the author of Pride and Prejudice. A thesis is not the whole essay: A thesis is your main idea/claim/refutation/problem-solution expressed in a single sentence or a combination of sentences.
Please note that according to the MLA Handbook for Writers of Research Papers, Seventh Edition, A thesis statement is a single sentence that formulates both your topic and your point of view (Gibaldi 42). Snow White! However, if your paper is more complex and to this Multi-faceted Problem requires a thesis statement, your thesis may require a combination of sentences. Make sure you follow these guidelines when creating your thesis: _____ The thesis/claim follows the guidelines outlined above. _____ The thesis/claim matches the requirements and goals of the White assignment. _____ The thesis/claim is clear and easily recognizable. _____ The thesis/claim seems supportable by good reasoning/data, emotional appeal. This resource outlines the generally accepted structure for introductions, body paragraphs, and conclusions in an academic argument paper. Keep in mind that this resource contains guidelines and not strict rules about organization.
Your structure needs to be flexible enough to meet the requirements of your purpose and duncan in macbeth audience. Body paragraphs: Moving from general to specific information. Your paper should be organized in Snow, a manner that moves from research general to Snow specific information. Every time you begin a new subject, think of an inverted pyramid - The broadest range of information sits at the top, and as the paragraph or paper progresses, the author becomes more and more focused on on Poverty: Solution to this Multi-faceted Problem the argument ending with specific, detailed evidence supporting a claim. Lastly, the White author explains how and why the information she has just provided connects to and supports her thesis (a brief wrap up or warrant). Image Caption: Moving from General to Specific Information. The four elements of a good paragraph (TTEB) A good paragraph should contain at least the following four elements: T ransition, T opic sentence, specific E vidence and analysis, and a B rief wrap-up sentence (also known as a warrant ) TTEB! A T ransition sentence leading in from a previous paragraph to assure smooth reading.
This acts as a hand off from one idea to the next. A T opic sentence that tells the reader what you will be discussing in the paragraph. Specific E vidence and analysis that supports one of your claims and that provides a deeper level of detail than your topic sentence. A B rief wrap-up sentence that tells the reader how and why this information supports the paper’s thesis. The brief wrap-up is also known as the and deductive warrant. Snow White! The warrant is important to your argument because it connects your reasoning and support to african and native american relations your thesis, and it shows that the information in Snow White Essay, the paragraph is related to essays your thesis and helps defend it. Supporting evidence (induction and deduction) Induction is the type of reasoning that moves from specific facts to a general conclusion. When you use induction in your paper, you will state your thesis (which is actually the conclusion you have come to after looking at all the White facts) and duncan then support your thesis with the facts.
The following is an example of Snow Essay induction taken from Dorothy U. Seyler’s Understanding Argument : There is the dead body of Smith. Smith was shot in his bedroom between the on Poverty: No Simple Problem hours of 11:00 p.m. and 2:00 a.m., according to the coroner. Smith was shot with a .32 caliber pistol. The pistol left in the bedroom contains Jones’s fingerprints. Jones was seen, by a neighbor, entering the Smith home at around 11:00 p.m. the night of Smith’s death. Snow White! A coworker heard Smith and Jones arguing in personal, Smith’s office the morning of the day Smith died. Conclusion: Jones killed Smith. Here, then, is the example in bullet form: Conclusion: Jones killed Smith Support: Smith was shot by Jones’ gun, Jones was seen entering the White Essay scene of the crime, Jones and Smith argued earlier in the day Smith died.
Assumption: The facts are representative, not isolated incidents, and thus reveal a trend, justifying the conclusion drawn. When you use deduction in an argument, you begin with general premises and move to Essay on Poverty: Solution to this Problem a specific conclusion. There is a precise pattern you must use when you reason deductively. This pattern is Snow called syllogistic reasoning (the syllogism). Syllogistic reasoning (deduction) is organized in three steps: In order for the syllogism (deduction) to work, you must accept that the relationship of the two premises lead, logically, to the conclusion. Here are two examples of deduction or syllogistic reasoning:
Major premise: All men are mortal. Minor premise: Socrates is a man. Conclusion: Socrates is why is waste a serious mortal. Major premise: People who perform with courage and clear purpose in a crisis are great leaders. Minor premise: Lincoln was a person who performed with courage and Snow White Essay a clear purpose in why is waste disposal of nuclear, a crisis. Conclusion: Lincoln was a great leader. So in order for deduction to work in Snow Essay, the example involving Socrates, you must agree that (1) all men are mortal (they all die); and (2) Socrates is african american relations a man. If you disagree with either of these premises, the Snow White conclusion is invalid.
The example using Socrates isn’t so difficult to validate. But when you move into more murky water (when you use terms such as courage , clear purpose , and great ), the connections get tenuous. For example, some historians might argue that Lincoln didn’t really shine until a few years into the Civil War, after many Union losses to Southern leaders such as Robert E. New Product Pricing Strategies! Lee. The following is a clear example of deduction gone awry: Major premise: All dogs make good pets. Snow White! Minor premise: Doogle is a dog. Conclusion: Doogle will make a good pet. If you don’t agree that all dogs make good pets, then the conclusion that Doogle will make a good pet is invalid. When a premise in duncan, a syllogism is missing, the syllogism becomes an enthymeme. Enthymemes can be very effective in Snow White, argument, but they can also be unethical and lead to invalid conclusions.
Authors often use enthymemes to persuade audiences. The following is an example of an enthymeme: If you have a plasma TV, you are not poor. The first part of the enthymeme (If you have a plasma TV) is the stated premise. Strategies! The second part of the statement (you are not poor) is the Snow White Essay conclusion. So the personal unstated premise is Essay “Only rich people have plasma TVs.” The enthymeme above leads us to an invalid conclusion (people who own plasma TVs are not poor) because there are plenty of people who own plasma TVs who are poor. Duncan In Macbeth! Let’s look at Snow White Essay this enthymeme in a syllogistic structure:
Major premise: People who own plasma TVs are rich (unstated above). Minor premise: You own a plasma TV. Conclusion: You are not poor. To help you understand how induction and deduction can work together to form a solid argument, you may want to inductive and deductive research look at the United States Declaration of Independence. The first section of the Declaration contains a series of syllogisms, while the Snow White Essay middle section is an inductive list of examples.
The final section brings the inductive and deductive research first and second sections together in a compelling conclusion. This resource outlines the generally accepted structure for introductions, body paragraphs, and Essay conclusions in an academic argument paper. Keep in inductive and deductive, mind that this resource contains guidelines and not strict rules about Snow White, organization. Waste Disposal Materials A Serious! Your structure needs to Snow White Essay be flexible enough to meet the requirements of your purpose and audience. In order to present a fair and convincing message, you may need to anticipate, research, and outline some of the common positions (arguments) that dispute your thesis. If the situation (purpose) calls for personal reflective you to do this, you will present and then refute these other positions in the rebuttal section of your essay. It is important to Snow White consider other positions because in most cases, your primary audience will be fence-sitters. Fence-sitters are people who have not decided which side of the argument to Essay on Poverty: No Simple Multi-faceted support.
People who are on Essay your side of the argument will not need a lot of information to align with your position. People who are completely against your argumentperhaps for ethical or religious reasonswill probably never align with your position no matter how much information you provide. Why Is Of Nuclear A Serious Problem! Therefore, the audience you should consider most important are those people who haven't decided which side of the Snow White argument they will supportthe fence-sitters. In many cases, these fence-sitters have not decided which side to align with because they see value in both positions. Therefore, to not consider opposing positions to of nuclear materials a serious problem your own in a fair manner may alienate fence-sitters when they see that you are not addressing their concerns or discussion opposing positions at all. Following the TTEB method outlined in White, the Body Paragraph section, forecast all the information that will follow in the rebuttal section and then move point by point through the other positions addressing each one as you go. The outline below, adapted from Seyler's Understanding Argument , is an example of inductive and deductive research a rebuttal section from a thesis essay. When you rebut or refute an White opposing position, use the following three-part organization: The opponent’s argument : Usually, you should not assume that your reader has read or remembered the argument you are refuting. Thus at No Simple to this Multi-faceted Problem the beginning of your paragraph, you need to state, accurately and Essay fairly, the main points of the argument you will refute.
Your position : Next, make clear the nature of your disagreement with the argument or position you are refuting. Your position might assert, for example, that a writer has not proved his assertion because he has provided evidence that is outdated, or that the argument is filled with fallacies. Your refutation : The specifics of your counterargument will depend upon the nature of your disagreement. If you challenge the writer’s evidence, then you must present the more recent evidence. If you challenge assumptions, then you must explain why they do not hold up. If your position is that the piece is filled with fallacies, then you must present and explain each fallacy. This resource outlines the and deductive generally accepted structure for introductions, body paragraphs, and conclusions in an academic argument paper. Keep in mind that this resource contains guidelines and not strict rules about organization. Your structure needs to be flexible enough to White meet the requirements of your purpose and and native relations audience. Conclusions wrap up what you have been discussing in your paper.
After moving from Essay general to specific information in the introduction and body paragraphs, your conclusion should begin pulling back into more general information that restates the main points of personal reflective your argument. Conclusions may also call for action or overview future possible research. The following outline may help you conclude your paper: In a general way, Restate your topic and why it is Snow White important, Restate your thesis/claim, Address opposing viewpoints and explain why readers should align with your position, Call for action or overview future research possibilities. Remember that once you accomplish these tasks, unless otherwise directed by your instructor, you are finished. Done. Complete. Don't try to bring in new points or end with a whiz bang(!) conclusion or try to pricing solve world hunger in Snow, the final sentence of your conclusion. Simplicity is best for to this Multi-faceted a clear, convincing message.
The preacher's maxim is one of the most effective formulas to follow for argument papers: Tell what you're going to tell them (introduction). Tell them what you told them (conclusion). Copyright 1995-2017 by The Writing Lab The OWL at Purdue and Purdue University. All rights reserved. Snow! This material may not be published, reproduced, broadcast, rewritten, or redistributed without permission.
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3 Resume Formats: How to Choose the Best One [Examples] Especially if it’s your first one? Your hands are hovering over the keyboard. You look at Essay, the blank Word document with the african and native, cursor pulsing in your face Now, what? What do you write? Where do you put the information? Wouldn’t it be great if there were road maps for resumes? Choosing the format of a resume is key to starting the resume writing process.
But it’s not as easy as it sounds. So, how do you choose a resume format put you ahead of the other job seekers? This article will tell you which resume format is White, right for you, and research, how to Snow, use the format of a resume to your advantage so that you stand out in a sea of other resumes. Duncan In Macbeth. Want to save time and have your resume ready in 5 minutes? Try our resume builder.
It’s fast and Snow White Essay, easy. Personal. Plus, you'll get tips while writing your resume. See templates and Snow White, create your resume here. How Do I Choose a Good Resume Format? Choosing the format of a resume is like shopping for an outfit for prom. Both the outfit and the format need to accomplish two things:
Show off your best assets. Essay On Poverty: Solution To This. Be unique and within a certain dress code at Snow, the same time. Just like everything else with resume writing, there are no black and white rules when it comes to choosing the format of a resume. To make things easy, there are three main types of personal reflective essays recognized and accepted resume formats. Each takes a different approach to the organization of the Snow White, information on your resume. And each resume format has strengths and weaknesses.
The three types of resume formats are: How do you know which one is best for you? The reverse-chronological resume format is for everyone. Your mom, your little sister, and personal reflective, your uncle can all use a reverse-chronological resume format. White Essay. The combination resume format is for people who want to show off their skills a little bit before jumping into their experience because they are either a career changer or a high-level professional. Pricing. The functional resume format , aka the skills-based resume format, is controversial and Snow, should be avoided by Essay to this Multi-faceted, everyone.
More on that later. Bonus: Download FREE ultimate checklist of 54 things you need to do before you send your resume. “Resume 101 Checklist.” Speaking of skills, find out what skills are the most desirable and how to put them on Snow White Essay, a resume. The guide has a great infographic too: What Skills to waste materials a serious problem, Put on a Resume? [Examples+ 6 Tips] The Usual Choice - The Reverse-chronological Resume. The reverse-chronological resume format is the most common format and can be used by virtually anyone applying for a job. Essay. It is the reflective, bread and butter of resume formats.
Benefits of the Reverse-chronological Format. 1. It’s standard. Recruiters are used to Snow White Essay, scanning this easy-to-read resume format. They will automatically know where your information is, and that you’ve sent a complete resume. 2. Applicant Tracking Systems (ATS) can read it too . It is pricing strategies, easy for the robots to find the different sections of Snow White Essay your resume when you use the on Poverty: to this, reverse-chronological format. 3. The reverse-chronological resume format puts an emphasis on work history and experience . If you are an average job seeker, your work history is Snow, where most of your relevant skills will be located. Weaknesses of the Reverse-chronological Resume Format. 1. It’s standard. Choosing this standard resume format is safe, but it will look like all of the other resumes in duncan in macbeth the pile.
So you will need to make an extra effort to catch a recruiter’s eye and showcase your skills and achievements. 2. The reverse-chronological format puts an emphasis on work history and Snow, experience. If you have large gaps in your work history or no experience then it may not be the best format for showing off your skills. The reverse-chronological resume format places an emphasis on your job history by putting it at the top of the resume under the contact information. On Poverty: No Simple Multi-faceted Problem. You start by listing your most recent work and follow with past jobs in a reverse chronological order - thus the name of the format. Think of it like eating dessert before you get your main course followed by White, an appetizer. And it’s great because starting with dessert at the top of your resume is a good way to on Poverty: No Simple Solution to this, catch the attention of the recruiter. Here is what a reverse-chronological resume format sample looks like.
We created it in Snow Essay our resume builder (you can make your resume here): As you can see in the resume format sample, the experience section comes first followed by the education section and other additional sections. Are you struggling with how to write a resume? Read our complete guide: So how do you dress up this standard resume format so that it works best for you and attracts attention? How To Improve Your Resume By Adding These 3 Sections. Here are three ways that you can dress up a boring, old reverse-chronological resume format: Add a resume summary or resume objective. Add achievements to your experience section. Add a Hobbies and Interests Section.
I recommend starting with a carefully constructed resume objective or a resume summary. Choose the resume objective if you are an entry-level applicant, changing your career, or have very little experience. All other professionals should opt for the resume summary. African And Native Relations. Resume objectives and summaries are confusing, and they are hard to write. Snow. So, we’ve written complete guides about writing resume summaries and personal reflective, objectives so that you don’t have to struggle anymore. We’ve also made examples for almost any profession so you can see a sample from your own field of expertise. The Only Way to Snow, Use Resume Objectives [20+ Examples] (read now) 7 Resume Summary Tips That Will Get You the Job [INFOGRAPHIC] (read now) Adding your achievements within the experience section as bullet points is a way to duncan, get your top accomplishments at the top of your resume. Pro Tip: Use the PAR (Problem Action Result) approach to writing about your achievements: In situation P (Problem) I did A (Action) which led to R (Result) . So to pick a completely random and made up example: My previous employer wanted to increase revenue (P) so I created a new marketing campaign on Facebook (A) which led to a 15% increase in sales and a 10% increase in revenue (R) . Finally, adding a hobbies and interests section will give recruiters a fuller image of you as a person.
While it may seem unprofessional to include such an informal section in Snow the format of a resume, a lot of businesses are beginning to look for candidates who will fit in and native american with their office culture. Your personal interests can make you more attractive and Snow White Essay, memorable to a recruiter, and signal that you would be a good fit for the company. If you want to find out personal essays more about the benefits of a hobbies and interests section and how to add one to your resume, you can read the article below. The Only Way To Put Hobbies Interests on a Resume [5 Tips] (read now) How to Use a Combination Resume Format to White Essay, Boost Skills. A combination resume format is the only real alternative to the reverse-chronological resume format. As the name implies, the combination resume format combines aspects of the other two resume formats, focusing on skills without throwing out the experience section. The experience section is still important and near the duncan, top of your resume just like in a reverse-chronological resume format. White. You start a combination resume format with a resume summary (aka Qualifications Summary). Your resume summary can be formatted as a paragraph or as a list of bullet points, and is a short, snappy introduction that highlights your career progress and skill set. Your experience section comes next.
Here is where the reverse-chronological and combination resume formats differ. And Deductive. With the combination resume format , you can emphasize your skills by Essay, grouping the bullet points under specific, skill-based subheadings. As you list your roles and responsibilities under each job, you can organize the bullet points like this: Cinderella Bootcamp (2009-01 - present) Her Royal Highness, Princess Event Organizer. Spearhead team building activities for groups of up to 10 housekeeping princesses. Head up and manage a team of 15 mice responsible for kitchen and housekeeping duties. Personal Essays. Project management involving the motivation of a team of 20+ bluebirds responsible for camp laundry, with a 10% increase in productivity after two months. Conduct webinars on how to wash dishes in glass heels. White. Orchestrate the creation of internal communications between different departments. In Macbeth. Responsible for organizing, writing, and Essay, communicating the african, daily schedules and activities of both staff and bootcamp participants. Pro Tip: Grouping your bullet points under such subheadings is also good for providing ATS with keywords . The emphasis that the combination resume format places on skills is what makes it a good choice for Snow White talented professionals, who have a lot of skills and experience, and career changers. Career changers are able to focus on skills that will translate from their old role or profession to their new one.
After the skills-based experience section, the combination format continues in why is waste of nuclear materials problem the same way as the Essay, reverse-chronological format: education and and deductive, additional sections. Why the Snow Essay, Functional Resume Format is Dysfunctional. A functional resume format takes the pressure off of your job history and refocuses on your skills and abilities. Materials A Serious. Sounds great right? In fact, the Snow Essay, format of a functional resume just throws job history out of the window. And Native Relations. On a functional resume, an experience section is reduced to a list of old, dusty employers at White, the bottom of the new product strategies, resume.
You can eliminate dates and your roles and responsibilities. The bulk of the resume becomes a place for showcasing your skills in any order you see fit. If you aren’t careful, it can look like a jumble of random skills listed under vague headlines like “customer service skills” or “leadership skills.” You do not have to White, link these skills with job experience or explain how you got them. So your leadership skills could come from being the oldest sibling in your family. And your awesome customer service skills could go all the way back to that time when you were five years old with a lemonade stand in your front yard. The fact that there is no specific information or proof that you learned your skills in any sort of job setting is the real weakness of the functional resume format. In Macbeth. The lack of White proof alone makes you look suspicious and could result in why is waste of nuclear a recruiter simply throwing out your resume.
There are experts that will tell you that it is Snow Essay, a good format for students , people who have gaps in their work history, or people who are changing their careers. But it just makes you look sneaky - like you’re hiding something. It is also not good for ATS because the robots can't scan your resume for dates or specific sections. I would recommend not using the functional resume format if you can avoid it. Duncan In Macbeth. Here's How to Choose a File Format - PDF Resume Vs. Word Resume. Should you save you create a PDF resume or a Word resume? The benefit of creating a PDF resume is that your resume formatting will not get messed up when it is White Essay, opened by a recruiter. It also gives you more creative freedom as you'd use platforms such as Photoshop or InDesign to create a PDF resume. At the same time, your resume may need to pass through Applicant Tracking System (ATS) software.
And some ATS software may have trouble reading a PDF resume. ATS does not like graphs or tables and requires plain text. African. In that case, a Word resume is probably a better choice. In any situation, having both formats on hand is best practice. Bonus: Download FREE ultimate checklist of 54 things you need to do before you send your resume. Snow White. “Resume 101 Checklist.” While there are not many resume formats to duncan, choose from, the White Essay, choice is important. Why Is Disposal Materials. The format of White Essay a resume really comes down to Essay to this Multi-faceted Problem, whether or not you want to focus on your skills or your career progression.
Either way, you have to find ways to overcome the White Essay, cookie cutter nature of resume formats without coloring too far out of the lines. You also have to make sure that a recruiter doesn’t take one look at the format of your resume and personal reflective essays, decide that you are trying to hide something. The best way to enhance a standard resume format is to improve each section and to place your most important skills and Essay, achievements near the top third of your resume. If you can open with a great resume summary, followed by strong skills, experience, and achievements sections, then you can make any old resume format work for you. African American. Do you have any questions about choosing the Essay, right resume format for your position? Is there anything else that should be included in the article? Leave a comment. Natalie is a writer at personal reflective essays, Uptowork.
She loves writing about resumes and eating tacos more than life itself. She spends her free time reading complicated novels and binge watching TV series.
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Free Essays on White, Should Teenagers Have A Curfew. Freedom A youth curfew in Oakland is a waste of inductive, time for a lot of Police. Crime is still the same with or without a curfew and a curfew would take away teenagers freedom. At night there's danger all around Oakland and you can hear the screaming and gunshots. Many teenagers have been killed lead to.
Effectiveness of Juvenile Curfews . Curfew is White Essay, a word that derived from the French word “courvrefeu”. The meaning of the word courvrefeu is “to cover fire”. Implicating that a curfew is a way to put something out or maybe to reduce something down. Duncan. Going back in time, curfews have been around since the. Curfews: Adolescence and Partial Curfew. ?Teenage Curfews Everyone has a different opinion when discussing the issues of White Essay, curfews . Councils across Britain have tried to come up with a strategy for disposal a serious problem, young teenagers to remain indoors between specified hours, typically at Snow Essay, night. Police forces are trying to impose that teenagers must have a curfew . Teenagers.
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After school activities are important. They often help us to meet new people; therefore, students don’t just have friends in school. teachers assigning essays and peers pressuring one into going against ones values and beliefs are all part of a teenagers life. Daily life is very hectic for most people, especially teenagers . White Essay. From school to extracurricular activities, it is hard for our lives not to be filled with external constructs. How Loneliness Affects Teenagers ? Medina. On Poverty: Solution Problem. Abstract Our society is facing a lot of problems these days.
Most teenagers are suffering from loneliness. Loneliness is simply the desire of being alone. Loneliness has some problems to teenagers . First, low self-esteem. Low self-esteem is due to Essay the lack. of law; nor deny to any person within its jurisdiction the equal protection of the american relations laws.
However, many cities and states in Snow White Essay the US currently enforce curfew laws that deny young teens under the age of 18 their right to be in public places or to drive after certain hours. These laws are punishing minors. either save you or hinder you- it all depends on personal reflective, the way you see it. Curfew is very famous to Snow Essay an adolescent and it has a lot of power. One perspective of curfew is that it cuts your fun short. Say you are at a party: you have to inductive leave by ten-thirty, but we all know most of the fun happens around eleven. Curfew Law There are many laws passed in today's society that have a foundation for protecting our youth. Of course, many of these laws are a target for controversy, but one these laws seems to have found itself at the top of the list. This law, in many peoples opinion, is a direct violation of our. Students Should Have Work Before Start Tertiary Education.
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Alcohol and inductive and deductive drug use are common among teenagers , for varied reasons. Alcohol. Driving Curfews Violating Teens Rights. Driving Curfews Violating Teens Rights A seventeen year old friend of mine headed home from work at 11:00 at night on Snow, a Thursday in the month of July. Wanting to raise enough money to go on american, a band trip to Florida, she needed to Snow Essay work long hours, needing money to pay for her car insurance, she. Do Curfews Keep Teenagers Out of Trouble. Do Curfews Keep Teens Out of Trouble Bryan Win Lee Liang Jun Yong Jie Peng, Calvin HELP University Curfews Keep Teens Out of waste disposal materials, Trouble Do curfews keep teenagers out of trouble? This topic has always been on the cover page of today's newspaper headlines and White a hot topic that has been discussed by. curfews doesn't keep teens out of personal reflective, trouble.
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But there is a war going on drugs in many states, and the laws are so absurd that they can put a person with marijuana possession or distribution. ? 1975- The DOT’s Fatality Analysis reporting system—in its first annual report on Snow Essay, vehicle deaths by age group– reveals that more than 8,700 teenagers died. In Macbeth. ? 1978- The number of teens dying in car crashes peaks at 9,940. ? 1980- Federal government tries to stop teen drinking and driving; . Social Networking Is Negatively Influencing Teenagers. think social networking is such a self-contradictory term to use for simple websites that have only succeeded in raising a new breed of socially awkward, paranoid teenagers . A frightfully widespread issue I have observed myself as a regular user of Facebook is cyber-bullying. Snow White Essay. This generation of young. Identifying which teacher was the best I’ve ever had is in macbeth, a very simple task, despite the array that I have to White choose from.
He was my history teacher for four years, taking me all the way through the basic knowledge of Nazi Germany to an in-depth study of Russian Tsarism and USSR Communism. What made. The Growing Issue of American Children and Teenagers Both Overweight and Obese. of American Children and personal reflective essays Teenagers Both Overweight and Obese In nearly every city in America, one will find thousands of people who are either obese or overweight. White. The numbers and inductive rates at which Americans are becoming or are obese or overweight are far greater than they should be. Why is it that in a. Curfew Hundreds of cities nationwide have set up and enforced strict curfews on Snow White, youths being in public at night or during the school day. Curfews were set to try and lower the youth crime rate.
Even though only one in duncan six violent youth crimes occur during the White curfew hours. Most violent crimes happen. A Survey Report on Bad Eating Habits of Hong Kong Teenagers. Introduction A survey on teenager life style bad eating habits was conducted last month. The purpose of the african and native american survey is to study the bad eating habits of teenagers in Hong Kong. Questionnaires were distributed to students of 3S and they were all returned. This report will summarize and discuss the result. registration.
I asked him why he had pulled me over, but he just kept repeating, “license and registration”. He took my license and didn’t mention the curfew until he saw the Snow White age on the license. Duncan In Macbeth. He told me the car would be towed, even though I pointed out my house, which was no more than 1 kilometer away. Teenage Curfews: with Them or Against Them. home after curfew , all of sudden your pulled over by the police and either arrested or ticketed for curfew violations. Then you think to Snow Essay yourself, I wasn't doing anything wrong.
This has become an increasing problem in America today. It is a shame for teenagers to get charged with breaking curfew and disposal of nuclear materials a serious they. The Rules Should Not Be Changed for a Graduated Driver. The rules should not be changed for Snow Essay, a graduated driver Every year around the reflective world there are more and Snow White more accidents with teenage drivers, should the pricing strategies rules be changed for a teen in the graduated driver program in PEI? Many of the G drivers on White, PEI find following a lot of these rules very difficult. ? YOUTH CURFEWS : PROTECTION OR PUNISHMENT Student Name CultureWorks Course: OC1 Writing Instructor: Matt Devlin Date: April 21, 2011 Youth Curfews : Protection or Punishment Should teens have a night curfew ? Over the past several years, in order to reduce juvenile. ensure a healthy and positive future for children. It is equally important that a parent leads by example.
Also, outside resources are important to have for extra help and guidance for single parents. First, creating a schedule and keeping it consistent is important to keep order in a household. increased teen crime the town’s people have proposed to set a curfew at local malls or recreational centers. I oppose this view. by strategies, setting a curfew would not solve anything because the teens that are already breaking the law are not going to listen to Snow White a curfew it would just cause other problems such. Teenage Wasteland “Drugs are easy to why is waste materials a serious get use to, but hard to Snow Essay get out of it” Are you a parent afraid your teenager may be at risk with drugs? Or do you already know your teen child has a problem with them? If yes, your not the only one in this situation, in a survey done to on Poverty: No Simple Solution to this Multi-faceted 30 MLSHS students, I found. SHOULD SPORTS FIGURES OR CELEBRITIES BE CONSIDERED ROLE MODELS. ? SHOULD SPORTS FIGURES OR CELEBRITIES BE CONSIDERED ROLE MODELS? NAME: ESSAY GRADE COURSE: TUTOR’S NAME: DATE OF SUBMISSION Should sports figures or celebrities be considered role models? Role models are considered as a probable cluster of people that are capable to leave.
Curfew Law in Arizona. White Essay. Many cities in the state of Arizona have put a curfew on all kids. Inductive And Deductive Research. Kids under the age of 16 cannot be out unsupervised between 10 pm and 5 am. Kids 16-18 cannot be out during 12 am to 5 am. Our country is a free country and allows parents to control their own kids how they. Should Cosmetic Surgery Be Abanned. The number of White, cosmetic surgeries have increased, according to the Washington Post, by 440% compared to the number in 1997.
The side effects and black market society has increased as well. Today, I brought up a question- should cosmetic surgery be allowed or not? My motion is to strategies restrict cosmetic surgery. usually associated with adults but alcohol abuse and alcohol dependence are not only adult problems. Alcohol is the most frequently used drug by teenagers in the United States. It affects a significant number of kids and young adults between the ages of 12 and 20, even though drinking under the age of. Family Curfews: Can Not Keep Teens Out of Trouble. freedom is Snow, human nature. Everyone wants to inductive have his or her own space and time to manage. When you were a teenager , you sought for independence and tried to decide by yourself, but when you become a parent, can you still remember to let your children be free and have faith in them?
Most parents will forget. abortion should be banned are condition that women are not pregnancy, health problem in mother, and social problem. Snow. First, the pregnancy without readiness because the teenagers has sexual relation “premature” because nowadays it has communication is easy and comfortable. African Relations. It make teenagers can getting. When a curfew is established the Snow effected people, who are the teenagers , are not asked for in macbeth, their vote or opinion, they are not being allowed to exercise their freedom of speech. Although some people believe that there should be a law made for children to be home at Snow Essay, a certain hour, government should not. Marijuana Should be Legalized Globally Marijuana is recognized by many people for it attributes. It has been and still is one of the most controversial and debated topics. This plant has been in existence since this earth was created millions of in macbeth, years ago, and White Essay helped humans to survive throughout different. English Should Be Taught from reflective Kindergarten in Public School. English should be taught from kindergarten in public school Nowadays English language has become more important than years ago, now we are living in a bilingual country in Snow Essay which is essential speak English to communicate with others.
By the way there are many schools that teach English from new product pricing strategies preschoolers. Children Do the Crime and Parents Do the Time. agree with that, but I also know that not everyone is White, perfect. Inductive. What if the parents have taken all the Snow Essay necessary steps of responsibility, and are involved in duncan their child’s life? Should the punishment be the Snow same for them? Should age be a factor? Courts can charge a child at age twelve as an adult. Are the.
Curfew Is Beneficial to Teenagers. Curfew is a set time which teenagers will have to schedule their activities around. Generally, this curfew doesn’t change and new product helps your teen to understand boundaries. It is a wonderful idea for teens to have curfews because it teaches them to be responsible and Essay also considerate of other people around. law has is getting sticter on juvenile deliquents.
Kids are now judged by their charges or what they do rather than their age and maturity. Juveniles should not be charged as adults because it is unfair, wrong, and does more damage than good, juveniles may not deserve to duncan in macbeth receive such harsh punishments. What problems do teenagers with Asperger’s syndrome face to Snow Essay achieve success in in macbeth school and how can they be helped? ?What problems do teenagers with Asperger’s syndrome face to achieve success in school and how can they be helped? Introduction In a culture where being social and Snow outgoing are prized above all else, it can be difficult, even shameful, to be different. For example if you have Asperger’s. But Asperger’s.
teenage curfew laws in American cities such as Dallas, Texas is a good idea. Such laws can decrease the juvenile crime rate and provide an opportunity for teens who are at risk to become delinquents to receive needed help. Pricing. Over the Snow past several years, One reason I believe that teenager curfew laws. SMOKING SHOULD BE BANNED IN PUBLIC PLACES The numbers of people who smoke have increased over pricing the years. Although smoking is a really bad habit, people still choose to Snow smoke. To prevent this stuation, governments and every single people have to do something and smoking should be banned in public places. Risk of duncan in macbeth, Teenagers Behind the Wheel.
Risk of Teenagers Behind the wheel Assignment Number: U05A1 Eric Anderson email@example.com BUS 3004 Developing a Business Perspective December 10, 2009 Introduction For this paper, I will address the dangers of teenage driving. Motor vehicle accidents remain the leading. Bad Behaviors Should Not Be Taught in White Essay School. Bad Behaviors Should Not be Taught in School The lessons I learned from the book Staying Fat for Sarah Byrnes are: suicide is how to deal with your emotions; people make fun of you because of the way you look; it’s OK to watch porn and masturbate; Christians are hypocrites; and you should do whatever.