Section: 7.3.2 PDU Session identity
Content: The following network procedures shall apply for handling an unknown, erroneous, or unforeseen PDU session identity received in the header of a 5GSM message (specified as the header of a standard L3 message, see 3GPP TS 24.007[ Mobile radio interface signalling layer 3; General Aspects ]  [11]): a) If the network receives a PDU SESSION MODIFICATION REQUEST message which includes an unassigned or reserved PDU session identity value, the network shall respond with a PDU SESSION MODIFICATION REJECT message including 5GSM cause #43 "invalid PDU session identity". b) If the network receives PDU SESSION RELEASE REQUEST message which includes an unassigned or reserved PDU session identity value, the network shall respond with a PDU SESSION RELEASE REJECT message including 5GSM cause #43 "invalid PDU session identity". c) Upon receipt of an UL NAS TRANSPORT message, the network takes the following actions: 1) If the Request type IE is set to "initial request" or "initial emergency request" and the message includes a reserved PDU session identity value, the network shall respond with a DL NAS TRANSPORT message with 5GMM cause #90 "payload was not forwarded"; 2) otherwise, if the message includes an unassigned or reserved PDU session identity value, the network shall respond with a DL NAS TRANSPORT message with 5GMM cause #90 "payload was not forwarded". d) If the network receives a 5GSM message other than those listed in items a) through c) above in which the message includes a reserved PDU session identity value or an assigned value that does not match an existing PDU session, the network shall ignore the message. The following UE procedures shall apply for handling an unknown, erroneous, or unforeseen PDU session identity received in the header of a 5GSM message: a) If the UE receives a 5GSM message which includes an unassigned or reserved PDU session identity value, the UE shall ignore the message. b) If the UE receives a 5GSM message which includes a PDU session identity belonging to any PDU session in state PDU SESSION INACTIVE in the UE, the UE shall respond with a 5GSM STATUS message including 5GSM cause #43 "invalid PDU session identity".