In one example, a network device external to a services complex injects a plurality of probe packets along service chains provided by the services complex, wherein each of the plurality of probe packets includes a first timestamp indicating a time at which the network device sent the respective probe packet. Each of a plurality of service nodes in the services complex modifies each of the plurality of probe packets by inserting a respective second timestamp indicating a respective time at which the respective service node processed the respective one of the plurality of probe packets. An analytics device aggregates probe report information received from each of the plurality of service nodes to determine one or more path monitoring metrics.