Content for  TS 23.284  Word version:  18.0.0

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.

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.

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.

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 succeeding/preceding node.

When an intermediate node or the GMSC server determines that local switching should be re-established it shall send the LCLS Status Change Request message with the LCLS-Status-Change IE set to "LCLS-Connection-Preparation" to the preceding and to the succeeding node. The intermediate node or the GMSC Server not initiating the LCLS re-establishment shall check if the requested LCLS Status is allowed or not and if it is allowed the intermediate node shall forward the received LCLS Status Change Request message. On receipt of the LCLS Status Change Request Acknowledge message with the LCLS-Status-Change IE set to "LCLS Connection Preparation" and a Result code IE from the preceding/succeeding node, the intermediate node or the GMSC Server not initiating the LCLS re-establishment shall forward message to the succeeding/preceding node. The Result code indicates whether LCLS Status Change Request is accepted or not. On receipt of the LCLS Status Update message with the LCLS-Status IE set to "LCLS Connected" from the preceding/succeeding node:

• the intermediate node or the GMSC Server not initiating the LCLS re-establishment shall forward the message to the succeeding/preceding node.
• the intermediate node or the GMSC Server initiating the LCLS re-establishment shall not forward the message.

When the LCLS Status Change Request message with the LCLS-Status-Change IE set to "LCLS Connection Preparation" is received from the succeeding (or preceding) node, the MSC Server shall check if the requested LCLS status is allowed or not and if it is allowed then the MSC Server shall send to BSS the LCLS-Connect-Control message with the LCLS-Connection-Status-Control IE set to "connect". The MSC server shall send LCLS Status Change Request Acknowledge message with the correct LCLS-Status-Change IE value and a Result code back to the preceding (or succeeding) node. The Result code indicates whether LCLS Status Change Request is accepted or not. At reception of the LCLS-Connect-Control Acknowledge message or the LCLS-Notification message with the LCLS-BSS-Status IE set to "Call is Locally switched with requested LCLS configuration", 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.

The BSS shall perform the same actions as described in clause 7.3.1.4.