WAN-Switchover with Off-Server Session Manager Machines

In some larger implementations, the CIC servers in a switchover pair might be located in separate data centers to provide greater resiliency if an incident occurs at one data center.A WAN connection typically separates these data centers, resulting in higher latency between the CIC servers than would occur in a typical co-located LAN-based CIC server switchover pair.This WAN-based switchover configuration is termed WAN-switchover and results in another Session Manager Architecture option.

In CIC 3.0, off-server Session Managers remained connected to the same CIC server when a switchover occurred to avoid connections to CIC over a high-latency WAN connection. Recent CIC testing indicates that the bandwidth utilization between CIC and Session Manager is much less than the bandwidth between Session Manager and the clients so, in the current release of CIC, the default switchover behavior for off-server Session Managers is always to connect to the primary CIC server. Customers are still allowed to use the subsystem mode (WAN switchover mode) for reasons other than what we tested. So in the current release of CIC, we still support running off-server Session Manager in subsystem mode.

In a WAN-switchover configuration, it is ideal that client connections to a Session Manager over a high-latency WAN connection are minimized. The off-server Session Managers can be assigned to a CIC location to match the location of the on-server Session Manager, or they can use any other configured location. When a client makes a connection, Session Manager returns information about all on-server and off-server Session Managers on that CIC configuration including the location assignment for each. In the case below, the list would include all four off-server Session Managers as well as the two Session Managers running locally on the CIC servers.

The list of Session Managers is ordered as follows: first by the off-server Session Managers assigned to the same Location entry as the station, then by the off-server Session Managers assigned to the same Location entry as the user, any other off-server Session Managers, the primary CIC server, and finally the backup CIC server. If none of the off-server Session Managers are available, the client uses the IP address (or addresses) of the “Host” value specified in the client to attempt to discover and connect to Session Manager.

Matching the Location entries of users or stations to the same Location entry configured for an off-server Session Manager is a strategy that administrators can use to ensure that clients connect to Session Manager over a low-latency connection. For more information about configuring Session Manager for switchover, see Configuring Session Manager Instances.

Once the client has cached the list of alternate servers, any future connection attempts by the client prefer off-server Session Managers, even when a new instance of the client process is being started.

For more information on the process of discovering and selecting a Session Manager, see Session Manager Discovery and Selection.