SIP即时消息RFC342.doc

SIP即时消息RFC3428 .........................45 TO.............................................................................................................45 From........................................................................................................46 1 Call-ID.....................................................................................................47 Cseq.........................................................................................................48 Max-Forwards......................................................................................48 Via............................................................................................................48 Contact...................................................................................................49 Supported 和 Require........................................................................50 0 附加信息部分........................................................................................50 8.1.2 发送一个请求...............................................................................................50 8.1.3 处理应答.......................................................................................................51 : transaction 层的错误.........................................................................52 未知的应答...............................................................................................52 Vias..........................................................................................................52 处理3xx应答..........................................................................................52 处理4xx应答..........................................................................................54 8.2 UAS特性..............................................................................................................55 8.2.1 方法判定.......................................................................................................56 8.2