中文摘要：

由IETF最年轻的工作组之一的SIP工作组发布的SIP相关标准已经成为通信和网络界的研究热点。SIP起初被作为建立互联网会议、电话、多媒体和其他类型的通信会议可选择的协议而提出，另外它还能被用于新型的通信服务，如即时短消息和应用级的跨网络移动通信及跨用户设备的通信。介绍了SIP相关标准、基本结构、功能特点及应用领域，并介绍了当前比较流行的几个开源SIP协议栈。

英文摘要：

Although only more than one year since session initiation protocol had been delivered, SIP has already become the research hotspot in telecommunication and network fields In the beginning, as an option protocol SIP was brought forward for Intemet conference, phone, multimedia and other communications conference buildup. On the other hand SIP can be used for new type communications, such as instant message and application layer communication which between different mobile or different customer equipment. In this paper,describes the SIP, basic structure, function, characteristic and application domain in detail and also presents several popular open source SIP stacks.