Section: 5.1.2 Types of 5GMM procedures
Content: Depending on how they can be initiated, three types of 5GMM procedures can be distinguished: a) 5GMM common procedures: 5GMM common procedure can always be initiated when the UE is in 5GMM-CONNECTED mode. The procedures belonging to this type are: 1) Initiated by the network: i) network-initiated NAS transport; ii) primary authentication and key agreement; iii) security mode control; iv) generic UE configuration update; v) identification; and vi) network slice-specific authentication and authorization; 2) Initiated by the UE: UE-initiated NAS transport. 3) Initiated by the UE or the network and used to report certain error conditions detected upon receipt of 5GMM protocol data: 5GMM status. b) 5GMM specific procedures: At any time only one UE initiated 5GMM specific procedure can be running for each of the access network(s) that the UE is camping in. The procedures belonging to this type are: 1) Initiated by the UE and used e.g. to register to the network for 5GS services and establish a 5GMM context, to update the location/parameter(s) of the UE: registration. 2) Initiated by the UE or the network and used to deregister from the network for 5GS services and to release a 5GMM context: de-registration. 3) Initiated by the UE and used to deregister from the network for 5GS services and to release a 5GMM context: eCall inactivity procedure. c) 5GMM connection management procedures: 1) Initiated by the UE and used to establish a secure connection to the network or to request the resource reservation for sending data, or both: service request. The service request procedure can only be initiated if no UE initiated 5GMM specific procedure is ongoing for each of the access network(s) that the UE is camping in. 2) Initiated by the network and used to request the establishment of an N1 NAS signalling connection or to request re-establishment of user-plane resources for the PDU session(s) associated with 3GPP access or to request re-establishment of user-plane resources of the PDU session(s) associated with non-3GPP access over 3GPP access; not applicable for the non-3GPP access network: paging. 3) Initiated by the network and used to request re-establishment of user-plane resources of the PDU session(s) associated with non-3GPP access over 3GPP access or to deliver 5GSM downlink signalling messages associated with non-3GPP access over 3GPP access, when the UE is in 5GMM-CONNECTED mode over 3GPP access and in 5GMM-IDLE mode over non-3GPP access; or Initiated by the network and used to request re-establishment of user-plane resources of the PDU session(s) associated with 3GPP access over 3GPP access or to deliver downlink signalling associated with 3GPP access over 3GPP access, when the UE is in 5GMM-CONNECTED mode over non-3GPP access, and when the UE is in 5GMM-IDLE mode over 3GPP access and not in MICO mode: notification. NOTE 1: In NB-N1 mode, the UE NAS using 5GS services with control plane CIoT 5GS optimization can wait for the lower layers to complete the transmission of the previous UL NAS TRANSPORT messages carrying control plane user data before providing subsequent NAS messages. Other implementations are possible. NOTE 2: When providing NAS messages to the lower layers for transmission, the UE NAS using 5GS services with control plane CIoT 5GS optimization can prioritize sending NAS signalling messages over the UL NAS TRANSPORT messages carrying control plane user data. How the UE performs this prioritization is implementation specific.