AS Failover

BroadWorks Application Server Failover Support

When the BroadWorks Application Server (AS) is ungracefully shutdown, any existing agent calls are maintained with limited media support and no call control. The redundant AS has no knowledge of the old calls and it does not inform CSTA Connector about those calls. At this point, the call information collected by CSTA Connector before the failover becomes desynchronized with the BroadWorks call information.

This scenario results in stuck calls that may prevent new calls from being distributed to the agents, who appear to be busy because of the stuck calls.

Call Synchronization

For call synchronization, BroadWorks introduces an extended usage for the existing CallSubscriptionEvent event. The CallSubscriptionEvent event always contains the latest known call information for the subscribed user. For AS Failover scenarios, BroadWorks distributes this event as an unsolicited event as soon as BroadWorks detects the user call state desynchronization due to the AS failover. The system behavior in regards of the voice path is described in the Broadsoft BroadWorks documentation.

CSTA Connector, from its side, may induce the CallSubscriptionEvent event distribution at any time by issuing an UpdateSubscriptionRequest request for a specific user. CSTA Connector invokes the UpdateSubscriptionRequest request upon receiving a CSTA Snapshot Device request from the CSTA client. The content of the CSTA Snapshot Device response is created using the information provided in the CallSubscriptionEvent event associated with the UpdateSubscriptionRequest request.

Previously, the CSTA Snapshot Device has been implemented as BroadWorks' response to the RetrieveCallIdInfoListRequest request. The request-response mechanism in BroadWorks may be not synchronized with the real-time CTI Event reporting. BroadSoft recommends using the CallSubscriptionEvent event to collect the call data and avoid any potential race condition between the event reporting and receiving responses on the BroadWorks request.

CSTA Connector uses the content of the CallSubscriptionEvent event to synchronize Connector's internal call configuration. CSTA Connector notifies its clients (T-Servers) through either a CSTA Event or CSTA Response to inform them about the changes in the call configuration. The LMS message, 37205, is generated for each call party that is not synchronized.