Theory And Implementation Of VoIP Based SIP Protocol

With the fast development of the Internet technology,VoIP(Voice over IP)as a new network service has become the most promising technology.VoIP is a service for sending voice,video and data communications over the Internet based on packet switch technology,which can meet various requirements of people.Nowadays,there are two standards for singnaling and control in VoIP field,namely ITU-T recommendation H.323 and the IETF delivery Session Initiation Protocol(SIP).The ITU-T recommendation the H.323 set of protocols is used to provide multimedia services on QoS or packet-based networks.H.323 provides interoperability between devices,High level applications,ISPs,it independent of network architecture ,operation system and hareware.H.323 supports muti-point function,muitlcast and bandwidth management.H.323 provides scalability solutions to support multi-point conference and net meetings between heterogeneous networks.Since H.323 raised earlier,it has been gotten diplomatic implementation.The Session Initiation Protocol is a signaling protocol developed by IETF(Internet Engineering Task Force).The lastest version is RFC3261.SIP need to interoperates with other protocols to build a completed network communication system,such as SDP,RTP,RTCP,DNS,etc. SIP is similar to other internet protocols, such as HTTP and SMTP, and shares some of its design principles.It support proxy server, redirect server, registrar server and location service.SIP URI is very much like the Email address:tom@sipforum.com. SIP is text-based format, which is the most advantage compared with other IP telephony standards.SIP's success stems from its simplicity and scalability, so it has fast development.This thesis focus on the VoIP architecture based on SIP protocol, it involves user agent, proxy server, redirect server and directory server,etc. It gives some introduce for how to realize the interworking between SIP system and PSTN, and compares the H.323 architecture with the SIP. The thesis also involves preliminary research and analyse on SIP authentication and security.oSIP and eXosip are currently popular open-sourced implementation of SIP which is OSIndependent.We design and implementation a simple user agent by the two libraries.Using the experimental environment to testing the communication between proxy server and third-party user agent.