详细可参考3GPP 23.228
4.2.7.1 SIPForking
FORK更好的解释就是分线器/路由器,由一个线缆然后分解成很多个用户。在SIP协议中概念也是类似的。
The IM CN subsystem shall have thecapability to fork requests to multiple destinations; thiscapability is subject to rules for forking proxies defined in IETFRFC 3261 [12].