Segmented performance monitoring of multi-stage ATM node

A multi-stage ATM node (20) comprises plural ATM switches (22) connected together in cascading fashion. A tagging unit (BP/TU) appends a tag (82) to a cell which is to be routed through the ATM node. The tag comprises, e.g., a transfer list (88) of destination addresses for switching of the cell through the ATM node. For monitoring purposes, a node performance monitoring manager (60) defines one or more segments of monitored cell travel through the plural ATM switches of the ATM node, and then selectively starts and stops monitoring with respect to the defined segment. A terminating monitoring unit at a terminating end of the segment uses the tag of a received cell to determine whether the received cell is subject to performance monitoring, and also prepares a termination unit report. The node performance monitoring manager further causes generation of monitoring management cells which also bear a tag, including a monitoring activation cell; a response cell; and a monitoring result cell. The monitoring result cell includes monitoring data. Selective starting and stopping of monitoring over a defined segment is facilitated by additional monitoring management cells which have either a start code or a stop code included in their tags.