7.2.3 Intermediate Node/GMSC Server Initiated

23.2843GPPLocal Call Local Switch (LCLS)Release 17Stage 2TS

7.2.3.1 Principles

When an intermediate node or a GMSC server determines that local switching should be disconnected it shall send the LCLS Status Change Request message indicating disconnection preparation to the preceding and to the succeeding node.

On receipt of LCLS Status Change Request message indicating disconnection preparation the originating or terminating MSC server shall send LCLS break request immediately to the associated BSS. When the acknowledge message is received from the BSS, the MSC server shall return LCLS Status Change Request Acknowledge message indicating disconnection preparation and a Result code indicating LCLS Status Change Request was accepted.

The BSS needs to receive the LCLS break request on both call legs before releasing local switching.

7.2.3.2 Intermediate Node/GMSC server actions

When an intermediate node or a GMSC server determines that local switching should be disconnected it shall send the LCLS Status Change Request message with the LCLS-Status-Change IE set to "LCLS-Disconnection-Preparation" to the preceding and to the succeeding node.

The intermediate node or the GMSC Server not initiating the LCLS break shall forward the received LCLS Status Change Request message with the LCLS-Status-Change IE set to "LCLS-Disconnection-Preparation".

On receipt of the LCLS Status Change Request Acknowledge message with the LCLS-Status-Change IE set to "LCLS-Disconnection-Preparation" and a Result code IE indicating LCLS Status Change Request was accepted from the preceding (or succeeding) node, the intermediate node or the GMSC Server not initiating the LCLS break shall forward message to the succeeding (or preceding) node.

On receipt of the LCLS Status Update message with the LCLS-Status IE set to "LCLS Not Connected" from the preceding (or succeeding) node:

– the intermediate node or the GMSC Server not initiating the LCLS break shall forward the message to the succeeding (or preceding) node.

– the intermediate node or the GMSC Server initiating the LCLS break shall not forward the message.

7.2.3.3 MSC server actions

When the LCLS Status Change Request message with the LCLS-Status-Change IE set to "LCLS-Disconnection-Preparation" is received from the succeeding (or preceding) node, the MSC Server shall send to the BSS the LCLS-Connect-Control message with the LCLS-Connection-Status-Control IE set to "Release LCLS". If in the related MGW the access side termination is isolated from the network side termination, the MSC Server shall request the MGW to through-connect the access side termination to the network side termination.

If the LCLS-Connect-Control Acknowledge message with the LCLS-BSS-Status IE set to "call is locally switched with requested LCLS configuration" is received, the MSC server shall send to the preceding (or succeeding) node the LCLS Status Change Request Acknowledge message with the LCLS-Status-Change IE set to "LCLS-Disconnection-Preparation" and a Result code IE indicating LCLS Status Change Request accepted.

At reception of the LCLS-Notification message with the LCLS-BSS-Status IE set to "the call is no longer locally switched", the MSC server shall send to the succeeding (or preceding) node the LCLS Status Update message with the LCLS-Status IE set to "LCLS Not Connected".

At reception of the LCLS-Connect-Control Acknowledge message with the LCLS-BSS-Status IE set to "the call is no longer locally switched", after sending the LCLS Status Change Request Acknowledge message, the MSC server shall send to the succeeding (or preceding) node the LCLS Status Update message with the LCLS-Status IE set to "LCLS Not Connected".

7.2.3.4 BSS actions

The BSS shall perform the same actions as described in clause 7.2.1.4.