7.3.1 MSC server Initiated

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

7.3.1.1 Principles

The following Re-establishment procedures describe the scenario when a node has requested an LCLS-break for a temporary period while applying a supplementary service or CN intervention and once completed wishes to resume the LCLS connection. If the node which broke the LCLS does not re-establish the LCLS via these procedures, LCLS can also be re-established by another interaction such as handovers (as specified in clause 8) or subsequent LCLS negotiations (e.g. due to supplementary service interaction). If a node in the path does not accept the LCLS Status Change Request (e.g. re-establishment) it shall respond with a LCLS Status Change Request Acknowledge message containing a Result Code IE set to "Status Change Request rejected", and not forward the LCLS Status Change Request to the succeeding (or preceding) node.

7.3.1.2 MSC server actions

7.3.1.2.1 LCLS re-establishment to the network side

The MSC server which initiates LCLS re-establishment shall send the LCLS Status Change Request message with the LCLS-Status-Change IE to the succeeding (or preceding) node to requests a change in LCLS Status in the CN.

Once the LCLS Status Change Request message with the LCLS-Status-Change IE set to "LCLS-Connection-Preparation" is received from the preceding (or succeeding) node, the MSC server shall check if the requested LCLS Status is allowed and shall send the LCLS Status Change Request Acknowledge message with the correct LCLS-Status-Change IE value and with a Result code back to the preceding (or succeeding) node. The Result code indicates whether LCLS Status Change Request is accepted or not.

7.3.1.2.2 LCLS re-establishment to the BSS

Once the LCLS-Status-Change Request message with LCLS-Status-Change IE or the LCLS-Status-Change Request Acknowledge message with the LCLS-Status-Change IE sent from the preceding (or succeeding) node is received, the MSC sever shall check if the requested LCLS Status is allowed or not and if it is allowed then the MSC Server shall send the LCLS-CONNECT-CONTROL message with LCLS-Connection-Status-Control set to "connect" to the BSS

7.3.1.2.3 LCLS Status update to the network side

Once the LCLS-Notification message or LCLS-Connect-Control-ACK message sent from BSS is received by MSC server, and if the received LCLS-BSS-Status indicates local switching, the MSC server shall send to the succeeding (or preceding) node the LCLS Status Update message with the LCLS-Status IE set to "LCLS Connected" if the same LCLS status update is not already received from the succeeding (or preceding) node..

7.3.1.3 GMSC server actions

Once the LCLS Status Change Request message with the LCLS-Status-Change IE sent from preceding (or succeeding) node is received, the GMSC sever shall check if the requested LCLS Status is allowed or not and if it is allowed the GMSC server shall forward the LCLS Status Change Request message with correct value to the succeeding (or preceding) node.

At the reception of the LCLS-Status-Change Request Acknowledge message from the succeeding/preceding node the GMSC server shall forward the received message to the preceding/succeeding node.

Once the LCLS-Status-Update message with the LCLS Status IE sent from preceding/succeeding node is received by GMSC server,

– the GMSC Server shall forward the message to the succeeding/preceding node if the same request is not already received from the succeeding/preceding node.

– the GMSC Server shall not forward the message if the same request is already received from the succeeding/preceding node.

7.3.1.4 BSS actions

On receipt of the LCLS-Connect-Control message with the LCLS-Connection-Status-Control IE set to "connect LCLS" the BSS may establish LCLS (following the principles described in clause 4.4) and notify the CN as described for LCLS call establishment.