Replica Dissemination and Retrieval Protocol Accuracy

The first performance indicator considered for SID evaluation is accuracy, defined as the ratio between the number of successful resource searches and the total number of searches in stationary scenarios with fixed nodes. No reiterations of the SID protocol are taken into account; searches are considered successful only if they find the needed IRPs by exploring the first retrieval direction. Mainly two tunable parameters have demonstrated to affect the SID accuracy value in stationary scenarios: the number i of nodes hosting IRPs (that is the number of nodes along the straight path where replicas are positioned) and the maximum number s of hops explored in the retrieval phase.

The tuning of i and s permits to trade the SID accuracy against its imposed message overhead. Figure 1 shows the results obtained over more than 1,000 simulations with i and s independently varying from 2 to 15 hops (in the case distribution/retrieval paths reach network boundaries before arriving at their maximum number of allowed hops, REDMAN automatically makes paths continuing with a new random direction back in the dense MANET). Each plotted value represents the average of 20 simulations where delegates, dynamically determined by REDMAN RD, distribute i IRPs, and randomly chosen clients look for a resource replica by exploiting an s-hop-limited query. The reported results show that, when i and s are greater than the diameter of the considered dense MANET, the accuracy overcomes 85%. In all simulations done, we have experienced that choosing i and s values approximately equal to the dense MANET diameter permits to achieve sufficient accuracy, with limited message overhead in both phases of SID-based IRP dissemination and RR.

Figure 1: SID accuracy while varying i and s