Page 2 Lecture Notes in Computer Science 2865 Edited by G. Goos ...

Evaluation of the AODV and DSR Routing Protocols 292.3 Earlier Comparisons of DSR and AODVSeveral attempts have been made to compare DSR and AODV with respect topath optimality among other measures. Broch et al. [2] use an internal mechanismof ns-2 to measure the path optimality for the routing protocols. Essentiallyan omniscient observer of the simulation stores the total number of mobilenodes and a table of shortest number of hops required to reach from one node toanother at a particular instant of time. This information is used to compute thedifference between the length of the actual path used between the source anddestination at a particular instant of time in the instantaneous snapshot of thenetwork graph. The approach in MERIT is different from [2] in that it considersthe entire history of the network topology for the duration of the data flow andthe cost of updating the routes to the destination.The studies in [2] show that DSR uses routes that are very close to optimalwhereas AODV finds a greater number of routes which are further apart fromthe optimal in the instantaneous topology.In [5], the authors compare the protocols DSR and AODV using several quantitativemetrics. The general conclusion is that for application oriented metricssuch as delay and throughput, DSR outperforms AODV in less stressful conditions,i.e., for a smaller number of nodes and/or lower mobility.3 The MERIT ToolFigure 1 shows a high level block diagram of the MERIT tool. The tool takes, asinput, a mobile graph as well as actual route traces for the routing protocol underconsideration. Once there is sufficient confidence in the ratio for one parameter,runs for other parameters may begin. From a sequence of MERIT ratios for agiven parameter, a spectrum is generated.manetRoutingProtocolMobile GraphActual PathsMERITToolMERITRatio/SpectrumMERITSpectrumVisualizationFig. 1. The MERIT tool.3.1 Simulation EnvironmentWe generate the input for the MERIT tool using an extended version of ns-2[14] because it has the ability to simulate MANETs [3] and provides a referenceimplementation of the DSR and AODV routing protocols.We create mobility scenarios as in [2], which include 20 nodes in a 1500 ×300 m 2 area in order to force the use of longer routes. In our scenarios, everynode has an omni-directional transmission radius of 250 m and moves using the