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

26 P. Narayan and V.R. SyrotiukThe MERIT framework [6,7] takes a new approach to routing protocol assessmentfor MANETs. In MERIT a protocol is compared to a theoretical optimumrather than to a competing protocol. In particular, the measure proposed is theMERIT ratio, the mean ratio of the cost of the route actually used by the protocolto the cost of the optimal mobile path under the same network history.Since we take a ratio, we believe that some of the dependencies on the simulatorcancel out, yielding an implementation independent measure. The MERIT spectrumis the ratio taken as a function of some network parameter, such as thenode velocity. MERIT is a scalable comparison methodology, since the MERITspectra for a protocol are computed once and then can be compared to spectraof other protocols directly, rather than requiring that protocols of interest beported to the same simulator.The definitions and theoretical foundations of the MERIT framework werelaid out in [6]. In this paper, we focus on the implementation of MERIT in thens-2 network simulator [14] and perform an evaluation of two well establishedMANET routing protocols. Specifically, we present MERIT spectra for the DynamicSource Routing (DSR) [11] and the Ad hoc On Demand Distance Vector(AODV) [16] routing protocols for several network parameters.The remainder of this paper is organized as follows. In Section 2 we overviewthe MERIT framework as well as the DSR and AODV routing protocols. Section3 details the MERIT tool, the implementation of the MERIT framework,describing the generation of a mobile graph in ns-2. We also describe how weextract the actual routes for each of DSR and AODV and use them to computea MERIT ratio for a given run. We then use the MERIT tool to produce spectrafor various parameters. These results are presented and discussed in Section 4.Conclusions and ongoing work are given in Section 5.2 Overview2.1 Overview of the MERIT FrameworkSince a MANET is a mobile network, MERIT models the history of networktopology changes over some time scale T by a sequence of graphs. A mobilegraph G = G 1 G 2 ...G T is defined as any sequence G i ,i =1,...,T, of graphswhere the vertices of G i correspond to the nodes in the network, and its edgescorrespond to communication links between nodes. Similar models with the goalto capture dynamics in graphs include [1,8,12].Given a mobile graph, a mobile path between a source-destination pair is definedas a path sequence P = P 1 P 2 ...P T where P i is a path in the correspondingG i between the same source-destination pair.It is assumed that a cost model, expressed as a weight function on edges,underlies each graph. The weight function w i (u, v) for graph G i is a function ofvertex pairs (u, v) such that{ m(u, v) if edge (u, v) exists in Giw i (u, v) =(1)∞ if edge (u, v) does not exist in G iwhere m(u, v) is the value of the link metric on the edge (u, v).