The Research And Implementation Of SIP And Its Security Mechanisms

This paper carries on the research of SIP and its security mechanisms. Based on the research, a secure and practical software platform of SIP stack is implemented.With the development of IP technology, various multimedia services based on IP networks are popularized rapidly. Signaling control protocol is absolutely necessary for the management of multimedia sessions. Session Initiation Protocol (SIP) is an application-layer signaling protocol used to establish, modify, and terminate multimedia sessions. Compared with H.323, SIP is more tightly integrated with Internet protocols and has a lot of advantages. Now SIP is widely used and attracting more and more attention.SIP system often works in an open and complex network environment, which leads to various kinds of security threats to SIP elements and messages. It's an important problem to solve that proper security mechanisms have to be designed to protect SIP networks.At first the analysis of the function, structure and work flow of SIP is given according to RFC3261, with emphasis on the layered protocol structure and key elements such as transaction, dialog and so on. On the basis of the research, a layered and modularized scheme is proposed and the SIP stack software is developed, including user agent, proxy and registrar, which make up of a whole SIP network.Then the security problems faced by SIP networks are discussed. Some security mechanisms are chosen to establish an integrated SIP security framework. The TLS, S/MIME, HTTP authentication mechanisms and their application in SIP system are studied in detail. Specially, a solution is designed for the deployment of SIP in large scale networks, which integrates SIP networks and AAA system with the help of EAP and HTTP EAP authentication. Finally, the security mechanisms are implemented on the platform of the SIP stack software.