Section: 7.3.6 Context Response
Content: A Context Response message shall be sent as a response to a previous Context Request message, in the scenarios identified in clause 7.3.5. Possible Cause values are specified in Table 8.4-1. Message specific cause values are: - "IMSI/IMEI not known" - "P-TMSI Signature mismatch" - "User authentication failed" - "Target access restricted for the subscriber" Based on the subscription profile, when the access to the target RAT is prohibited for the subscriber, the old MME/SGSN/AMF may reject the Context Request message with the cause "Target access restricted for the subscriber". When the source MME/SGSN/AMF supports one or more of the CIoT optimization features as indicated through the CIoT Optimizations Support Indication IE specified in clause 8.125, and if the target node is a MME and the target MME has not set the AWOPDN bit of the CIoT Optimizations Support Indication IE set to 1 in the Context Request message as specified in clause 8.125, the source MME/SGSN/AMF shall reject the Context Request with a cause value of "Request Rejected" under the following conditions (conditions are mutually exclusive): - If the UE is attached to the source MME/SGSN without any PDN connection through the SGW and PGW and without any SCEF PDN connection; - if the UE is attached to the source MME/SGSN with only the PDN connection(s) of PDN type "non-IP", through the SGW and the PGW but the UE has not activated any SCEF PDN connection and the target MME/AMF has not set the SGNIPDN bit of the CIoT Optimizations Support Indication IE set to 1 in the Context Request message as specified in clause 8.125; - if the UE is attached to the the source MME/SGSN with only the SCEF PDN connection(s) but the UE has not activated any PDN connection through the SGW and PGW and the target MME has not set the SCNIPDN bit of the CIoT Optimizations Support Indication IE set to 1 in the Context Request message as specified in clause 8.125; - if the UE is attached to the source MME/SGSN with only PDN connection(s) of PDN type "non-IP", through the SGW and the PGW and at least one SCEF PDN connection and the target MME has neither set the SGNIPDN bit nor the SCNIPDN bit of the CIoT Optimizations Support Indication IE set to 1 in the Context Request message as specified in clause 8.125; - if the UE is registered to the source AMF without any PDU session; - if the UE is registered to the source AMF with only PDU session(s) of type "Unstructured" or "Ethernet", and the target MME has not set the SGNIPDN bit of the CIoT Optimizations Support Indication IE set to 1 in the Context Request message as specified in clause 8.125. NOTE 2: Among the CIoT optimization features, only the support of SCEF Non-IP PDN connection and the support of SGi Non-IP PDN connection are applicable to a SGSN. NOTE 3: 5GS supports Attach without PDU session. 5GS can also support Unstructured and Ethernet PDU session types, which are assimilated to "SGi Non-IP PDN connections" over N26 if Ethernet PDN connection type in EPC is not supported; otherwise, the Ethernet PDU session in 5GS can move to EPC seamlessly. If the target node is a MME and the target MME has not set the ETHPDN bit in the Indication IE to 1 in the Context Request message as specified in clause 8.12, or the target node is a SGSN, the source MME shall reject the Context Request with a cause value of "Request Rejected" if the UE is attached to the source MME with only PDN connection(s) of PDN type "Ethernet". Table 7.3.6-1 specifies the presence requirements and conditions of the IEs in the message. Table 7.3.6-1: Information Elements in a Context Response Table 7.3.6-2: MME/SGSN/AMF UE EPS PDN Connections within Context Response The Bearer Context shall be coded as depicted in Table 7.3.6-3. Table 7.3.6-3: Bearer Context within MME/SGSN/AMF UE EPS PDN Connections within Context Response Table 7.3.6-4: Remote UE Context Connected within MME/SGSN UE EPS PDN Connections within Context Response Table 7.3.6-5: MME/SGSN UE SCEF PDN Connections within Context Response Table 7.3.6-6: PGW Change Info with Context Response