Improving the performance of query-based routing protocols through "diversity injection"

In this paper, we investigate the diversity properties of routes acquired through traditional route query floods. The on-demand nature of query-based (reactive) routing is appropriate for networks with dynamic network topologies (such as ad-hoc networks). An intrinsic feature of route query protocols is the support for multiple route replies. While it is widely assumed that the set of discovered routes is fairly diverse, an examination of the query propagation behavior reveals that these routes typically have many nodes/links in common. Without sufficient diversity, the routing protocol is limited in its ability to promptly recover from (or even prevent) interrupted service caused by route failures. Based on our understanding of query propagation behavior, we propose a novel mechanism that uses information from terminated query threads to "inject" diversity into the collection of route replies. We study the impact of our diversity injection scheme on the demanding ad-hoc networking environment. Our results demonstrate how diversity injection can leverage a small investment of temporary cache to reduce both the rate of route failures and the bandwidth consumed by overhead query traffic.