Section: 5.5.1.3.6A Mobility and periodic registration update for an emergency services fallback not accepted by the network
Content: If the mobility and periodic registration update request triggered upon receiving a request from the upper layers to perform an emergency services fallback: - fails due to an abnormal case described in subclause 5.5.1.3.7, the UE shall perform the procedures as described in subclause 5.5.1.3.7; - cannot be accepted by the network as described in subclause 5.5.1.3.5, the UE shall perform the procedures as described in subclause 5.5.1.3.5; or - fails due to receiving the AUTHENTICATION REJECT message, the UE shall perform the procedures as described in subclauses 5.4.1.2.2.11, 5.4.1.2.3.1, 5.4.1.2.3A.1 or 5.4.1.3.5. If the mobility and periodic registration update request triggered upon receiving a request from the upper layers to perform an emergency services fallback fails due to abnormal case b) in subclause 5.5.1.3.7, the UE shall inform the upper layers of the failure to access the network. NOTE 1: This can result in the upper layers requesting implementation specific mechanisms, e.g. procedures specified in 3GPP TS 24.229[ IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3 ]  [14] can result in the emergency call being attempted to another IP-CAN. If the mobility and periodic registration update request triggered upon receiving a request from the upper layers to perform an emergency services fallback fails due to abnormal cases c), d), e) or g), cannot be accepted or fails due to receiving the AUTHENTICATION REJECT message and the UE does not attempt to select an E-UTRA cell connected to EPC or 5GCN as described in subclause 5.5.1.3.5 and the UE is camped on NR or E-UTRA cell connected to 5GCN in the same PLMN where the last mobility and periodic registration update request was attempted, the UE shall inform the upper layers of the failure of the procedure. NOTE 2: This can result in the upper layers requesting implementation specific mechanisms, e.g. procedures specified in 3GPP TS 24.229[ IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3 ]  [14] can result in the emergency call being attempted to another IP-CAN.