Techniques are disclosed for improved monitoring and analysis of VoIP communications, multimedia communications or other types of network traffic in a network-based communication system. In accordance with one aspect of the invention, endpoint devices of the network-based communication system are configurable so as to collectively implement a distributed monitoring and analysis system which does not require a centralized testing server or other centralized controller. Distributed test units associated with the endpoint devices may be utilized in implementing the distributed monitoring and analysis system, and are preferably configured to support a web-based user interface providing access to measurement data. The endpoint devices may be advantageously organized into a hierarchy comprising a plurality of zones, with each of the endpoint devices belonging to at least one zone. For each zone, one of the endpoint devices may be designated as a zone leader for controlling the periodic generation of communications between selected endpoint devices that belong to subzones of that zone in the hierarchy.