说明：  osip实现RFC3261，全部用C语言实现，跨平台编译，小巧，简单易懂，但是没有实现UA的能力；eXosip实现了UAA的基本功能，是一种基于osip实现的。两个库唯一的缺点就是性能差了一些，不太适合服务器产产品的开发，但是适合终端的开发。
(osip achieve RFC3261, all using C language, cross-platform compilation, compact, easy to understand, but not the ability of UA eXosip achieve the basic functions of the UAA is a based on osip achieve. Two libraries only drawback is the poor performance of some, not suitable for the development of server products production, but for the development of the terminal.)