Section: 5.31.2 Preferred and Supported Network Behaviour
Content: At registration, a UE includes its 5G Preferred Network Behaviour indicating the network behaviour the UE can support and what it would prefer to use. NOTE: If the UE supports S1-mode then the UE will indicate the supported EPS Network Behaviour Information in the S1 UE network capability IE. The 5G Preferred Network Behaviour signalled by the UE includes the following information in the 5GMM Capability IE: - Whether Control Plane CIoT 5GS Optimisation is supported. - Whether User Plane CIoT 5GS Optimisation is supported. - Whether N3 data transfer is supported. - Whether header compression for Control Plane CIoT 5GS Optimisation is supported. And the following 5G Preferred Network Behaviour in other IEs: - Whether Control Plane CIoT 5GS Optimisation or User Plane CIoT 5GS Optimisation is preferred. If N3 data transfer is supported is indicated by the UE, the UE supports data transfer that is not subject to CIoT 5GS Optimisations. If the UE indicates support of User Plane CIoT 5GS Optimisation then it shall also indicate support of N3 data transfer. The AMF indicates the network behaviour the network accepts in the 5G Supported Network Behaviour information. This indication is per Registered Area. The AMF may indicate one or more of the following: - Whether Control Plane CIoT 5GS Optimisation is supported. - Whether User Plane CIoT 5GS Optimisation is supported. - Whether N3 data transfer is supported. - Whether header compression for Control Plane CIoT 5GS Optimisation is supported. If the AMF indicates support of User Plane CIoT 5GS Optimisation then it shall also indicate support of N3 data transfer. If the UE and AMF indicate support for User Plane CIoT 5GS Optimisation, the AMF indicates support of User Plane CIoT 5GS Optimisation support for the UE to NG-RAN. For NB-IoT UEs that only support Control Plane CIoT 5GS Optimisation, the AMF shall include support for Control Plane CIoT 5GS Optimisation in the Registration Accept message. A UE that supports the NB-IoT shall always indicate support for Control Plane CIoT 5GS Optimisation. A UE that supports WB-E-UTRA shall always indicate support for N3 data transfer. The 5G Preferred Network Behaviour indication from the UE may be used to influence policy decisions that can cause rerouting of the Registration Request from an AMF to another AMF.