Section: Create Session Response
Content: The Create Session Response message shall be sent on the S11/S4 interfaces by the SGW to the MME/S4-SGSN, on the S5/S8 interfaces by the PGW to the SGW, on the S2b interface by the PGW to the ePDG, and on the S2a interface by the PGW to the TWAN as part of the procedures listed for the Create Session Request (see clause 7.2.1). A PGW may receive the Create Session Response message sent from another PGW (see clause 7.2.1), the PGW shall forward the Create Session response message to the SGW as received from another PGW but with the following modifications: - the destination IP address and UDP port of the message shall be set to the source IP address and UDP port of the Create Session Request message received from the SGW; - the source IP address and UDP port of the message shall be set to the IP address and port of the forwarding PGW. In some network deployment, e.g. when 5G Network Slice is deployed and the combined PGW-C/SMFs are connected to the UDM, if the MME indicated in the Create Session Request that it supports PGW redirection due to mismatch with network slice subscribed by UE, the source PGW/SMF may select another PGW supporting the network slice for which the UE has a subscription and then reject the Create Session Request with the cause set to "PGW mismatch with network slice subscribed by the UE" and with the FQDN or IP address of the other PGW that the MME should use for establishing the PDN connection. NOTE: This can be used e.g. if there is no GTPv2/UDP/IP connectivity between PGW/SMFs pertaining to different network slices, or if the source PGW/SMF does not support forwarding the request to the target PGW/SMF as specified in clause 7.2.1. If handling of default bearer fails, then cause at the message level shall be a failure cause. Possible Cause values are specified in Table 8.4-1. Message specific cause values are: - "Request accepted". - "Request accepted partially". - "New PDN type due to network preference". - "New PDN type due to single address bearer only". - "Missing or unknown APN". - "GRE key not found". - "Preferred PDN type not supported". - "All dynamic addresses are occupied". - "Remote peer not responding". - "Semantic error in the TFT operation". - "Syntactic error in the TFT operation". - "Semantic errors in packet filter(s)". - "Syntactic errors in packet filter(s)". - "User authentication failed". - "APN access denied – no subscription". - "APN Restriction type incompatibility with currently active PDN Connection". - "Version not supported by next peer". - "Denied in RAT". - "Protocol type not supported". - "APN congestion". - "Multiple PDN connections for a given APN not allowed". - "Multiple accesses to a PDN connection not allowed". - "Context not found". - "UE not authorised by OCS or external AAA Server". - "PGW mismatch with network slice subscribed by the UE". Table -1: Information Elements in a Create Session Response Table -2: Bearer Context Created within Create Session Response Table -3: Bearer Context marked for removal within a Create Session Response Table 7.2.2-4: Load Control Information within Create Session Response Table 7.2.2-5: Overload Control Information within Create Session Response Table 7.2.2-6: PGW Change Info within Create Session Response