Registration Accept and GUTI allocation

The AMF Confirms Registration

The Registration Accept message is the AMF's confirmation that the UE has successfully registered. It contains essential information the UE needs to operate on the network. The most important element is the 5G-GUTI, a temporary identity composed of the GUAMI (which identifies the serving AMF through MCC, MNC, AMF Region ID, AMF Set ID, and AMF Pointer) plus the 5G-TMSI (a temporary subscriber identity). The AMF allocates a fresh GUTI at each registration to prevent tracking the subscriber through a static identifier.