SIP协议正逐渐取代H．323，成为IP电话服务的核心信令协议。举例说明了SIP网络中安全隐患，接着讨论了SIP采用

的安全机制及其适用条件。在此基础上，提出现有安全机制的问题及端至非端安全问题。-SIP protocol is gradually replaced by H. 323, to become the core of IP telephone service signaling protocols. Illustrated SIP network security risks, and then discussed the use of SIP security mechanisms and their application conditions. On this basis, the existing security mechanisms and end-to-non-client security issues.