目前可用的IPv4地址已经分配了70％左右，而且B类地址已经基本耗尽。而采用长度为128字节IP地址的IPv6协议，则彻底解决了IPv4地址不足的难题，并且在地址容量、安全性、网络管理、移动性以及服务质量等方面有明显的改进，IPv6也成为下一代互联网络协议采用的核心标准之一-Currently available IPv4 addresses have been allocated about 70 , and the Class B addresses have basically been

The present document specifies the signalling procedures for accessing the 3GPP Evolved Packet Core network and handling the mobility between 3GPP and non-3GPP accesses via the S2c reference point defined in 3GPP TS 23.402 [3]. The present document