Research And Design Of A VoIP System Based On P2P-SIP Technology

Peer-to-Peer (P2P) and SIP (Session Initiation Protocol, SIP) are the most popular topics in Internet now. As a most famous VoIP protocol, SIP attracted much attation in telecommunication operaors. SIP-based VoIP systems can not only handle the communication system in a low-cost way, but also facilitate the service provider to provide their customers with value-added services.P2P brings a revolution in both ideologic and computing model. Peer-to-peer (P2P) systems inherently have high scalability, robustness and fault tolerance because there is no centralized server and the network self-organizes itself. This is achieved at the cost of higher latency for locating the resources of interest in the P2P overlay network.This paper is concerned about how effective the combination of SIP and P2P. To change the original C/S architecture to a Peer-to-Peer SIP-VoIP communication networks, and at the same time, all of the Network user nodes can have the original type and quality of services. The paper explains the SIP entity, the information structure and the Chord algorithm of P2P in detail, then have a detail description of both architecture and modular design, at the last, have some partial realization of the system.The most key uses distributed robust and scalable key lookup of distributed hash table (DHT)-based structured P2P algorithms - Chord.It uses SIP as the underlying protocol so that it interoperates with existing infrastructure such as SIP-PSTN gateways.Our architecture for peer-to-peer Internet telephony using the Session Initiation Protocol (SIP) supports basic user registration and calls setup as well as advanced services such as offline message delivery, voice video mails and multi-party conferencing. In this paper, it describes the design and implementation of the P2P-SIP node, using pseudo code and example messages. In particular, the paper cares about the following questions: (1) how to implement a P2P-SIP node for basic functionality? (2) How to use a P2P-SIP node for existing user agents? and (3) how to extend it for advanced features such as firewall traversal?Our modular design allows reusable and replaceable components. The open architecture allows installing new services without affecting the existing design.