Research On Distributed SIP Protocol Stack And The Implementation

SIP is a session control protocol emerges in recent years, which origin from internet domain and has a deep impact on telecommunication architecture. Other than traditional telecommunication protocol, SIP employed totally text-based encoding, which make it easy to manipulate the protocol message by script language as the http message, and depend on intelligent terminal as well as ALL-IP transport. The IP Multimedia subsystem introduced by 3GPP's R5 specification take SIP as the only session control protocol covered the user access, call control and service logic execute layer. Accordingly, SIP has been developed to support correspondent capabilities. At the recent years, IETF make more effort on SIP's research and extension, as a result, SIP can meet various demands from the different layer of the telecommunication network. SIP can execute complex session control together with the SDP (Session description protocol), in the other hand, it also can carry application specific information such as instant message and presence status etc. by message body, in latter case, it is rather a transport protocol than a application one.The main contributions of this dissertation are summerized as follows:Firstly,take a study on the SIP network architecture and session control capabilities. The advantages and disadvantages of the layered network and full-mesh network are assessed, and its impact on the SIP stack architecture is analyzed.Secondly, by the research on load balance method of distributed SIP system, a new distributed architecture is present which apply to the end-to-end signal characteristic of the SIP protocol. Theoretically, this architecture can lead to ideal load balance result.Thirdly, combined with the HASH-based load-balance algorithm and appropriative SIP extension, a new distributed fault-tolerant algorithm is introduced. The algorithm has much more benefit over exist ones.Fourthly, the 3GPP IMS specifications introduce the many-to-many relation-ship between PUI and PVI,it's has an obvious influece on the performance of distributed SIP systems and the result under different distributed key is assessed.