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

As computer communication techniques progress rapidly, VoIP becomes a mainstream of voice information transmission in NGN. Being an important signaling protocol of VoIP, SIP is one of the research hotspots of multimedia communication due to its simplicity, agility and strong expansibility. In spite of the maturation of network conferencing technique based on SIP, the most of conferencing systems operate on the basis of C/S mode, which need more resources of servers to store information and coordinate communication. Therefore, it is easy to result in problems of system bottleneck.DHT-based structured P2P network is good at expansibility, robustness and self-organization, so it can avoid problem of single failure brought by server under traditional C/S mode. Consequently, by combining the advantages of P2P and SIP, introduction of P2P technique into SIP-based VoIP teleconferencing can make it possible to realize decentralized network conferencing system with no more special servers.After a thorough study on P2P network with decentralized structured topology, this paper designs and implements a VoIP teleconferencing system based on P2P-SIP. Main work and study of this paper are the following:The paper analyzes SIP protocol, CHORD logical structure and CHORD algorithms in detail, and gives a combination design of P2P and SIP. It also discusses and implements the necessary extensions to SIP protocol to support VoIP teleconferencing based on P2P-SIP.After studying and comparing the most SIP-based network conferencing models, the paper chooses a conferencing model of signaling centralized and media data distributed on the basis of centralized conference management.Logical system framework of VoIP teleconferencing based on P2P-SIP has been given and the main system modules are designed and implemented. Furthermore, the author studies SOFIA-SIP open source library and GSM audio function library, and hereby implements the corresponding code into VoIP teleconferencing system. The system test and performance analysis are also executed.Aim at the needs of large-scale conferencing systems, the paper proposes a new scheme of teleconferencing systems based on layered services and application layer multicast, and discusses an alternative design of VoIP teleconferencing.The paper analyzes and improves the adjacency measurement method of CTAG., and discusses the application layer multicast tree strategy design, as well as its performance analysis.