1. 欢迎大家订阅和关注，精讲3GPP通信协议（2G/3G/4G/5G/IMS）知识点，专栏会持续更新中.....敬请期待！ 目录 1. Attach(23.401 5.3.2) 2. Service Request(23.401 5.3.4) 3. TAU (23.401 5.3.3) 3.1 Tracking Area Update procedure with Serving