Research And Application Of Session Initiation Protocol

With NGN times arrivals, Internet tends to provide more much better added value service, Internet interface has developed for the simplicity and isomerism platform, the major part of it has all adapted to text-based communication protocol. For example, HTTP, SMTP Protocol. Under such background, the SIP (Session initial Protocol) protocol has appeared. This protocol which is similar with HTTP and brought forward by IETF ((Internet Engineering Task Force)), is easy to communicate with each others. SIP protocol is easy to be integrated with internet enveroment. The SIP protocol is a new agreement, which has poured a kind of new power into Internet-based VOIP system. Therefore, the SIP agreement and relevant technology research which have applied much more popular at present are also kinds of key technologies on future for a new VOIP system realization.Sip protocol brought forward by IETF is a kind of control protocol of application layer. SIP is used to create, change and terminate a multimedia session involved several terminations. SIP protocol can make the communication between telecom application and internet application going well. The grammar of SIP protocol is based on the grammar of internet, it provides multimedia application based on IP protocol, and it is mostly hopeful for future application. Therefore, the choice of picking SIP protocol as signal protocol to develop multimedia software is more and more popular.According to the logic function of the application of SIP in the Multimedia conversation, the system is constituted by four kinds of Communication elements, the user agent, the SIP proxy server, the redirection server and the SEP register server. This research work Analysis each part of SIP system respectively, especially the SIP Protocol, the Session Description Protocol(SDP), Real-time Transport Protocol(RTP) and its Processes.We focus on how to design a user agent based on OSIP and what is the function of SIP protocol and its relevant technology. The UA runs on Windows and OSIP is its base layer.Under the Windows environment, the SIP source codes, based On the C++ Program, are compiled and are running successfully. The result shows a voice communication demo based on SIP Protocol. Finally, this research is based on the IP network components, the main objective is to analyze, with the help of flow chart, how the SIP control Protocol and a collection of other Protocols such as SDP, RTP and RTCP Protocols are locked together to Process SIP call.