Section: 7.2.11.3 Downlink Data Notification Failure Indication
Content: A Downlink Data Notification Failure indication shall be sent from an MME/SGSN to a SGW indicating that the UE did not respond to paging. It shall also be sent in the case that the UE responded to the page with a Service Request but that the MME has rejected the request by sending a Service Reject to the UE. It may happen, for example, because the requested service is not supported or there is a bearer context mismatch. Additionally, a Downlink Data Notification Failure indication shall be sent in case the UE has rejected the page as specified in clause 4.3.33 in 3GPP TS 23.401[ General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access ]  [3]. This message should not be used after an MME/SGSN successfully receives the Service Request message from the UE in the Network Triggered Service Request procedure as defined in the 3GPP TS 23.401[ General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access ]  [3]. NOTE: Either the Modify Bearer Request message or the Delete Bearer Command message is used by the MME/SGSN to indicate a possible failure case after an MME/SGSN successfully receives the Service Request message from the UE. Possible Cause values are: - "UE not responding". - "Service denied". - "UE already re-attached". - "Rejection due to paging restriction". Table .3-1 specifies the presence of the IEs in the message. Table .3-1: Information Elements in a Downlink Data Notification Failure Indication