name: STA
full_form: Session Termination Acknowledgement
context: The multicast service deactivation is a signalling procedure that will terminate the user registration to a particular MBMS multicast service. The multicast service deactivation can be initiated by the GGSN, when indicated so by the UE, or by the BM-SC, for service specific reasons.
  Figure 32: MBMS Service deactivation procedure
  1.	The UE sends an IGMP (IPv4) or MLD (IPv6) Leave message over the default PDP context to leave a particular multicast service identified by an IP multicast address.
  2.	The GGSN sends a STRÂ to the BM-SC, indicating that the UE is requesting to leave the multicast service. The session to be terminated is uniquely identified by the Diameter session-id.
  3.	Upon reception of the STR, the BM-SC verifies that the IP multicast address corresponds to a valid MBMS bearer service and sends a STA to the GGSN that originated the Leave Indication. The APN shall be the same that was provided during service activation (see " Service Activation" procedure).
  4.	Upon reception of the STA the GGSN sends an MBMS UE Context Deactivation Request to the SGSN. The IP multicast address, APN and IMSI together identify the MBMS UE Context to be deleted by the SGSN. The APN is the one received in step 3.
  5.	The GGSN receives a Delete MBMS Context Request (NSAPI). This GGSN may be different from the GGSN that receives IGMP Leave request in step 1.
  6.	The GGSN deletes the MBMS UE Context and sends a STRÂ to the BM-SC to confirm the successful deactivation of the MBMS UE Context.
  7.  The BM-SC, then, deletes the MBMS UE Context and sends a confirmation to the GGSN in a STA message.
  8.	If the GGSN does not have any more users interested in this MBMS bearer service and the "list of downstream nodes" in the corresponding MBSM Bearer Context is empty, the GGSN initiates a De-Registration procedure as specified in 17.5.5.
  9.	The BM-SC confirms the operation by sending a STA message to the GGSN as specified in 17.5.5.
description: The STA message is used by the BM-SC to acknowledge and confirm the successful termination of an MBMS session.
explanation: STA is a Message Type because it confirms and acknowledges the completion of a session termination request.
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biotag_Description: O,B-Message,O,O,O,O,O,B-Network Function,O,O,O,O,O,O,O,O,O,B-Service,O