Abstract: A telephony system having a router for telephony calls has a plurality of selectable routing protocols and a system monitoring facility adapted for periodically determining the condition and performance of the system. Routing protocols are selected according to one or both of system condition and performance. In a system subject to degradation of performance under certain conditions, routing protocols may be selected that are relatively immune to causes of degradation in performance. As performance degrades, escalatory selection of more simple routing protocols may be provided.