A Topology-Aware Relay Lookup Scheme for P2P VoIP System

Because of the best-effort service in Internet, direct routing path of Internet may not always meet the VoIP quality requirements. Thus, many researches proposed Peer-to-Peer VoIP systems such as SIP+P2P system, which uses relay node to relay RTP stream from the source node to the destination node and uses application-layer routing scheme to lookup the best relay nodes. The key of those systems is how to lookup the appropriate relay nodes, which we call relay lookup problem. This paper presents a novel peer relay lookup scheme based on SIP+P2P system. The main ideas are to organize the P2P network using a Cluster overlay and to use topology-aware to optimize relay selection. We introduce the mechanism in detail, and then evaluate this mechanism in NS2 network simulation environment. The results show that our scheme is scalable and can get high relay hit ratio, which confirm the feasibility of a real system. We also make comparison with traditional schemes and the results show that our scheme has good path quality.