Telephone conversations carried over an internet protocol network or other asynchronous network can be monitored for quality and rerouted if the error rate of data transmission through the network exceeds some predetermined threshold value. One or more counters in a switching system along a pathway records the occurrence of missing, delayed, or out of sequence cells or data packets over time. At some predetermined threshold value, considered to be an excessive error rate, the switching system can be used to trigger a rerouting of the telephone call or subsequent calls to pathways with better error rates and therefore better transmission quality.