Abstract-In this article, we present CodeCast, a network coding based ad hoc multicast protocol. CodeCast well-suited especially for multimedia applications with low loss, low latency constraints such as audio/video streaming. The key ingredient of CodeCast is random network coding which transparently implements both localized loss recovery and path diversity with very low overhead. Simulation results show that in a typical setting, CodeCast yields near 100% delivery ratio as compared to 94% delivery ratio by traditional multicast. More importantly, the overhead is reduced by as much as 50%.

Mobile ad hoc networks (MANETs) are vulnerable to routing attacks, especially attacks launched by non-cooperative (selfish or compromised) network members and appear to be protocol compliant. For instance, since packet loss is common in mobile wireless networks, the adversary can exploit this fact by hiding its malicious intents using compliant packet losses that appear to be caused by environmental reasons.In this paper we study two routing attacks that use non-cooperative network members and disguised packet losses to deplete ad hoc network resources and to reduce ad hoc routing performance. These two routing attacks have not been fully addressed in previous research. We propose the design of "self-healing community" to counter these two attacks. Our design exploits the redundancy in deployment which is typical of most ad hoc networks; Namely, it counters non-cooperative attacks using the probabilistic presence of nearby cooperative network members.To realize the new paradigm, we devise localized simple schemes to (re-)configure self-healing communities in spite of random node mobility. We develop a general analytic model to prove the effectiveness of our design. Then we implement our secure ad hoc routing protocols in simulation to verify the cost and overhead incurred by maintaining the communities. Our study confirms that the community-based security is a cost-effective strategy to make off-the-shelf ad hoc routing protocols secure.

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