Performance Comparison of Ad Hoc Network Routing Protocols Presented by Venkata Suresh Tamminiedi Computer Science Department Georgia State University

Abstract In recent years, a variety of new routing protocols are designed for routing in Ad hoc networks. But little performance information on each protocol and no realistic performance comparison between them is available. This presents the results of a detailed packet-level simulation comparing four algorithms : DSDV, TORA, DSR and AODV.

Methodology OVERALL GOAL : To measure the ability of the routing protocols : To measure the ability of the routing protocols : 1. To react to network Topology Changes. 2. Successfully Deliver data packets. SCENARIO FILE : 1. Exact motion of each node. 2. Exact sequence of packets. 3. Time at which each change in motion or or packet origination is to occur. or packet origination is to occur.

Movement Model  Pause Time : Each node remains stationary for pause time seconds and then moves to a random destination. Each node remains stationary for pause time seconds and then moves to a random destination.  Different Pause Times : 0, 30, 60, 120, 300, 600 and 900 seconds. 0, 30, 60, 120, 300, 600 and 900 seconds.  Movement Patterns : We consider 10 different movement patters for each value of pause time, giving 70 different patterns. giving 70 different patterns.  Consideration of Combination of Pause Times ???

Communication Model Parameters to Consider : Parameters to Consider : 1. Packet generation rate of the nodes (CBR). 2. Sending rates of the nodes. 3. Size of the packets. Varying the packet generation rate of the nodes is equivalent to varying the sending rate. Varying the packet generation rate of the nodes is equivalent to varying the sending rate. Fix the sending rate to 4 packets/second and vary the packet generation rates between 10, 20 and 30 packets/second – resulting 210 different scenarios. Fix the sending rate to 4 packets/second and vary the packet generation rates between 10, 20 and 30 packets/second – resulting 210 different scenarios.

Communication Model (contd…) Concern with 1024-byte packets : Due to lack of Spatial Diversity, it is resulting to Congestion, which is a problem for all protocols as none of the protocols performs Load Balancing. Concern with 1024-byte packets : Due to lack of Spatial Diversity, it is resulting to Congestion, which is a problem for all protocols as none of the protocols performs Load Balancing. All communications are peer-to-peer and connections were started at times uniformly distributed between 0 and 180 seconds. All communications are peer-to-peer and connections were started at times uniformly distributed between 0 and 180 seconds. Problem with TCP Sources ??? Problem with TCP Sources ??? Varying Sending rates of nodes ??? Varying Sending rates of nodes ???

Scenario Characteristics Lengths of routes to deliver packets. Lengths of routes to deliver packets. Internal mechanism calculates the shortest path and the packet is labeled with this information, which is compared with no.of hops actually taken. Internal mechanism calculates the shortest path and the packet is labeled with this information, which is compared with no.of hops actually taken. The height of each bar represent the no.of packets for which the destination was the given distance away when the was originated. The height of each bar represent the no.of packets for which the destination was the given distance away when the packet was originated.

Scenario Characteristics (contd…) Total No.Of. Topology changes in each scenario. Total No.Of. Topology changes in each scenario. One link connectivity change is counted whenever a node goes into or out of direct communication range with another node. One link connectivity change is counted whenever a node goes into or out of direct communication range with another node.

Metrics Packet delivery ration : The ratio between the no.of packets originated by the “application layer” source and the no.of packets received by the destination. Packet delivery ration : The ratio between the no.of packets originated by the “application layer” source and the no.of packets received by the destination. Importance : Importance : Describes the loss rate. Describes the loss rate. i.e. describes the Maximum throughput. i.e. describes the Maximum throughput. Characterizes both Completeness and Correctness of the routing protocol. Characterizes both Completeness and Correctness of the routing protocol.

Metrics (contd…) Routing Overhead : The total no.of routing packets transmitted during the simulation. For packets sent over multiple hops, each transmission of the packet counts. Routing Overhead : The total no.of routing packets transmitted during the simulation. For packets sent over multiple hops, each transmission of the packet counts. Importance : Importance : Measures the scalability of a protocol. Measures the scalability of a protocol. Degree to which it will function in congestion. Degree to which it will function in congestion. Efficiency in terms of consuming node battery power. Efficiency in terms of consuming node battery power.

Metrics (contd…) Path Optimality : The difference between the no.of hops a packet took to reach its destination and shortest path existed when it originated. Path Optimality : The difference between the no.of hops a packet took to reach its destination and shortest path existed when it originated. Importance : Importance : Ability of the routing protocol to efficiently use network resources. Ability of the routing protocol to efficiently use network resources. Considering Delay as Metric ??? Considering Delay as Metric ???

Simulation Results Summary : Delivery Ratio : Delivery Ratio : All of the protocols deliver to a greater percentage, converging to 100% when there is no node motion. All of the protocols deliver to a greater percentage, converging to 100% when there is no node motion. DSR and AODV-LL perform particularly well, delivering over 95% irrespective of mobility. DSR and AODV-LL perform particularly well, delivering over 95% irrespective of mobility. DSDV-SQ fails to converge at pause times less than 300secs. DSDV-SQ fails to converge at pause times less than 300secs.

Simulation (contd…) Routing Overhead Routing Overhead Overhead of on-demand protocols drops as the mobility drops. Overhead of on-demand protocols drops as the mobility drops. DSDV-SQ overhead is nearly constant with respect to mobility rate. DSDV-SQ overhead is nearly constant with respect to mobility rate. DSR has the least overhead and TORA has the Maximum overhead. DSR has the least overhead and TORA has the Maximum overhead.

Simulation (contd…) Packet Delivery Ratio Details : This is studies as a function of “Node Mobility” and “Network Load”. Packet Delivery Ratio Details : This is studies as a function of “Node Mobility” and “Network Load”.

Packet Delivery Ratio (contd…)

DSR and AODV-LL are independent of offered traffic load, with both protocols delivering between 95% and 100%. DSR and AODV-LL are independent of offered traffic load, with both protocols delivering between 95% and 100%. DSDV-SQ fails to converge below pause time 300, and does poorly dropping to 70% at higher rates of mobility. DSDV-SQ fails to converge below pause time 300, and does poorly dropping to 70% at higher rates of mobility. This maintains only one route per destination and consequently, each packet that the MAC layer is unable to deliver is dropped as there are no alternate routes. This maintains only one route per destination and consequently, each packet that the MAC layer is unable to deliver is dropped as there are no alternate routes.

Packet Delivery Ratio (contd…) TORA does well with 10 and 20 sources but not with higher load. TORA does well with 10 and 20 sources but not with higher load. The majority of packet drops are due to the creation of short-lived routing loops that are natural part of its link-reversal process. The majority of packet drops are due to the creation of short-lived routing loops that are natural part of its link-reversal process. Avoid allowing packets to loop until their TTL expires, as the looping data packets interfere with the ability of other nearby nodes to successfully exchange the broadcast UPDATE packet that will resolve their routing loop. Avoid allowing packets to loop until their TTL expires, as the looping data packets interfere with the ability of other nearby nodes to successfully exchange the broadcast UPDATE packet that will resolve their routing loop.

Routing Overhead Details

Routing Overhead (contd…)

Shape of Curves (DSR/AODV): Shape of Curves (DSR/AODV): DSR and AODV-LL, using similar mechanisms have almost identically shaped curves. DSR and AODV-LL, using similar mechanisms have almost identically shaped curves. Both exhibit that incremental cost of additional sources decreases as sources are added. Both exhibit that incremental cost of additional sources decreases as sources are added. As they use information learned from one route discovery to complete a subsequent route discovery. As they use information learned from one route discovery to complete a subsequent route discovery.

Routing Overhead (contd…) Absolute Overhead (DSR/AODV) Absolute Overhead (DSR/AODV) AODV-LL requires 5 times the overhead of DSR when there is constant node motion. AODV-LL requires 5 times the overhead of DSR when there is constant node motion. Because each of its route discoveries propagates to every node in the ad hoc network. Because each of its route discoveries propagates to every node in the ad hoc network. DSR limits the overhead of packets. DSR limits the overhead of packets. By using caching from forwarded and promiscously overheard packets. By using caching from forwarded and promiscously overheard packets. By using non-propagating ROUTE REQUESTS. By using non-propagating ROUTE REQUESTS.

Path Optimality Details

Path Optimality (contd…) A difference of 0 means the packet took a shortest path, and a difference greater than 0 indicates the no.of extra hops the packet took. A difference of 0 means the packet took a shortest path, and a difference greater than 0 indicates the no.of extra hops the packet took. Above figure aggregates the data from all pause times into one. Above figure aggregates the data from all pause times into one. DSDV-SQ and DSR do very well regardless of routing with respect to node mobility rate. DSDV-SQ and DSR do very well regardless of routing with respect to node mobility rate. TORA and AODV-LL show a significant difference with respect to pause time. TORA and AODV-LL show a significant difference with respect to pause time.

Lower Speed of Node Movement Packet Delivery Ratio : All perform well. Packet Delivery Ratio : All perform well.

Lower Speed (contd…) Overhead Overhead Protocols are not challenged as overhead increases very mildly. Protocols are not challenged as overhead increases very mildly. DSR’s caching is even more effective at lower speeds. DSR’s caching is even more effective at lower speeds.

Conclusion DSDV : DSDV : This performs quite predictably, delivering virtually all data packets when node mobility rate and movement speeds are low, and failing to converge as mobility increases. This performs quite predictably, delivering virtually all data packets when node mobility rate and movement speeds are low, and failing to converge as mobility increases. TORA : TORA : The worst performer, still delivers over 90% of the packets with 10 or 20 sources. At 30 sources its performance is worst as max no.of packets are dropped. The worst performer, still delivers over 90% of the packets with 10 or 20 sources. At 30 sources its performance is worst as max no.of packets are dropped.

Conclusion (contd…) AODV AODV Performs almost as well as DSR at all mobility rates and movement speeds but the Overhead is more as the mobility increases. Performs almost as well as DSR at all mobility rates and movement speeds but the Overhead is more as the mobility increases. DSR DSR Very good at all mobility rates and movement speeds, although its use of source routing increases the no.of routing overhead, its caching is used very optimally. Very good at all mobility rates and movement speeds, although its use of source routing increases the no.of routing overhead, its caching is used very optimally.