Adaptive SIP-based Peer-to-Peer VoIP System Design and Implementation
In recent years,VoIP applications are growing rapidly.However,the commonly used offer/answer mechanism cannot work properly in the environment where network address translators(NAT) are massively deployed.Current solutions rely on STUN,in which heartbeat messages would periodically be sent out to maintain the mapping between the public and private addresses.The state of maintaining heartbeat messages would become a huge burden to the VoIP server.We design and implement an adaptive SIP-based peer-to-peer communication system that supports VoIP over NATs.The system extends the SDP offer/answer model to share the public and private IP addresses and ports of both media ends at the call establishment of a session.We demonstrate its feasibility through the implementation of a real system.We evaluate the effectiveness of our proposed scheme and show that our system has a better performance when compared to other VoIP applications that use the supernode-relay mechanism.