7.3 Gateway MSC Server Procedures

23.2313GPPRelease 17SIP-I based circuit-switched core networkStage 2TS

7.3.1 Call Clearing received from peer SIP-I node

If a release indication (CANCEL, BYE, final error response (4xx, 5xx or 6xx) for the initial INVITE request) is received from the preceding or succeeding node, and the GMSC server decides to release the call, the GMSC server shall:

a. process those request according to SIP procedures for a user agent towards the preceding or succeeding side as specified in IETF RFC 3261 [15], and initiate a call release towards the succeeding or preceding node acting as user agent as specified in IETF RFC 3261 [15], or

b. perform the following procedures:

1. If the GMSC receives a CANCEL request from the preceding node, the GMSC shall send a 200 OK (CANCEL) response for the CANCEL request to the preceding node. If the GMSC did not yet receive a final response for the initial INVITE request from the succeeding node, the GMSC shall then initiate a CANCEL request to the succeeding node.

2. If the GMSC server receives a BYE request from the preceding/succeeding node, the GMSC shall perform the procedure described in Clause 7.3.4 to release seized MGW resources, and forward the BYE request to the succeeding/preceding node. The GMSC server will then receive a 200 OK(BYE) response from the succeeding/preceding node and shall forward this 200 OK(BYE) response to the preceding/succeeding node.

3. If the GMSC server receives a final error response (4xx, 5xx or 6xx) for the initial INVITE request from the succeeding node, the GMSC server shall perform the procedure described in Clause 7.3.4 to release seized MGW resources, and then forward a final error response (either the received response or an error reponse resulting from internal mapping procedures) to the preceding node.

Note: The procedures under bullet b.are similar to SIP proxy procedures, as specified in IETF RFC 3261 [15] , with the exception that the GMSC server sets SIP headers (e.g. contact, via) in forwarded SIP messages consistent with earlier settings during the dialogue.

The GMSC shall also perform the procedure described in Clause 7.3.4 to release seized MGW resources

7.3.2 Call Clearing initiated by G-MSC Server

7.3.2.1 Call clearing to the destination side

If the call is already established or under establishment towards the destination, call clearing to the destination side from the GMSC server is performed as described for the originating MSC server in clause 7.2.3.2.

7.3.2.2 Call clearing to the originating side

Call clearing to the originating side from the GMSC server is performed as described for the terminating MSC server in clause 7.2.3.2.

7.3.3 Call Clearing received from MGW

7.3.3.1 Bearer released on the destination side

After the GMSC server received the Bearer Released procedure from the MGW on the destination side, call clearing to the destination side and the originating side from the GMSC server is performed as described for the originating MSC server and for the terminating MSC server in clause 7.2.3.2 respectively.

7.3.3.2 Bearer released on the originating side

After the GMSC server received the Bearer Released procedure from the MGW on the originating side, call clearing to the originating side from the GMSC server is performed as described for the terminating MSC server in clause 7.2.3.2. If the call is already established or under establishment towards the destination side, call clearing to the destination side is performed as described for the originating MSC server in clause 7.2.3.2.

7.3.4 Call Clearing procedures towards MGW

The (G)MSC server shall release any MGW allocated resources reserved for the call. If any resources were seized in the MGW the MSC server shall use the Release Termination procedure to indicate to the MGW to remove the bearer termination.