Permanent data connections are well suited for Communication Manager when ISDN-PRI endpoints are used. Permanent data connections, such as interconnections between local area networks (LANs), are always active during business hours. The ISDN end-to-end monitoring and the ability of the endpoint to react to failures provide for critical availability of data. With ISDN, endpoints can detect network failures and initiate backup connections through the server. ISDN endpoints can also establish additional calls when extra bandwidth is needed.

Any failures that Communication Manager does not automatically restore are signaled to the endpoint application. The endpoint application can initiate backup data connections over the same PRI endpoint. Communication Manager routes the backup data connections over alternate facilities if necessary.