Adaptive Path Accumulation for Reactive Routing Protocols

We study the overhead of some mechanisms for information dissemination. We use reactive routing protocols in mobile ad hoc networks as our illustrative example. However, while reactive routing protocols are the main application for our results, they apply to different settings as well, which include publish/subscribe information dissemination mechanisms, information dissemination in sensor networks, and location services. We use a performance measure, defined in [8], which we call the efficiency xi of the information dissemination process, and use this efficiency to evaluate the overhead. The overhead is influenced by the use of a mechanism to increase the amount of information disseminated, at the cost of a higher overhead, called path accumulation. We compare the overhead of routing protocols with and without path accumulation. We observe that path accumulation is always more efficient at disseminating route information in the network, but the gain in efficiency decreases when it is normalized by the number of extra routes discovered, as more is known about the network. This means that the marginal return of path accumulation decreases over not using path accumulation. We propose a new route discovery mechanism which applies to most of the reactive protocols using a route request/route reply exchange. Our route discovery mechanism, denoted adaptive path accumulation adjusts the accumulated path in order to either: scale its bandwidth overhead down as more information is distributed in the network, or improve the network discovery by carefully selecting the routes to be propagated. We assess a range of adaptive path accumulation policies using numerical evaluation and show the effect of these policies on route discovery and packet overhead.