Section: Change Notification Response
Content: The Change Notification Response message may be sent on the S11/S4 interface by the SGW to the MME/SGSN and is sent on the S5/S8 interface by the PGW to the SGW as part of location dependent charging related procedures to acknowledge the receipt of a Change Notification Request. If SGW does not support the feature (see clause 7.3.14 "Change Notification Request"), SGW may silently discard Change Notification Request message from MME/SGSN. If the MME/ SGSN does not receive Change Notification Response, the MME/SGSN may either send Change Notification Request to the same SGW next time UE location changes, or not (marking SGW as not supporting the feature). The Cause value indicates whether or not the Change Notification Request was received correctly. Possible Cause values are specified in Table 8.4-1. Message specific cause values are: "Request accepted". "Request accepted partially". "IMSI/IMEI not known". In this version of the specification, the sender shall set the header TEID value to that of the peer node's Control Plane TEID on S11/S4 interface or to the peer node's Control Plane TEID on S5/S8 interface. However a receiver shall be prepared to receive messages in which the header TEID value is set to zero from implementation conforming to earlier versions of this specification. When that is the case, the receiver identifies the subscriber context based on the included LBI, IMSI, and/or MEI IEs. If the IMSI is unknown, or the IMEI is unknown when the UE is emergency attached and UICCless or the UE is emergency attached but the IMSI is not authenticated for the receiving GTP-C entity, then the message shall be silently discarded and no further processing of the IEs shall continue. If the MME/SGSN receives Change Notification Response containing a Cause value of "IMSI/IMEI not known" and CS bit set to 1, this indicates that the associated PDN connection does not exist within the PGW. The Change Reporting mechanism shall be stopped in the receiving SGSN/MME for all Bearers of the associated PDN connection. The SGSN/MME shall then initiate PDN disconnection for all of these PDN Connections. If the PDN Connection associated of the Change Notification Request message received by the SGW does not exist within the SGW, the SGW shall return Change Notification Response with the CS bit set to 0 to the MME/SGSN. The Change Reporting mechanism shall be stopped in the receiving SGSN/MME for all Bearers of the associated PDN connection, and the MME/SGSN shall then locally delete the PDN connection and release all associated resources. If the location Change Reporting mechanism is to be stopped or modified for this subscriber in the SGSN/MME, then the PGW shall include the Change Reporting Action IE in the message and shall set the value of the Action field appropriately. If the MME has sent the "MO Exception Data Counter" for the RRC Cause "MO Exception data" in the Change Notification Resquest, the MME shall reset the counter value when receiving the Change Notification Response message. Table -1: Information Element in Change Notification Response