A Peer-to-Peer SIP System based on Service-Aware Transport Overlays

Abstract

The Session Initiation Protocol (SIP) traditionally establishes and manages its sessions with centralized servers, which have been challenged by issues with TCP/IP networks right from its beginning, for instance, issues with NAT traversal or network congestions. On the other hand, there are peer-to-peer and overlay techniques that potentially can make SIP working better under various network conditions. Overlay networks can provide a good abstraction from the real network, thus hiding the presence of NATs. Some proposals on peer-to-peer SIP have been recently presented. While these proposals attempted to solve a subset of challenges faced by traditional SIP, such as removing the centralized SIP entities, there is to the best of our knowledge no single solution offering a comprehensive view of the peer-to-peer SIP architecture and operation. This paper presents a novel approach for a peer-to-peer SIP system, using overlay techniques for signalling and media transport in the Internet. This system is based on the Ambient Networks Service- Aware Transport Overlay (SATO) system. The proposed system replaces the traditional SIP proxy/registrar function with a distributed lookup mechanism, adding overlay functionality to the SIP signalling and to the RTP traffic. Moreover, different from previous proposals, our approach deliberately places media/ packet relays into the SIP/RTP paths, which allows an efficient session management and media communication.