If you can't see into the VoIP traffic on your network, then you don't know whether it's good or bad. To know whether voice-quality or call-connect issues are related to your VoIP IP/PBX system or are tied to underlying network issues, you'll need to turn to the evolving class of network monitoring products called voice-over-IP analysis tools.

Since our last test of these tools, VATs have picked up more monitoring power and offer a deeper level of detail in their displays regarding the VoIP activity of your network. Degradation of your VoIP traffic can be monitored, investigated and resolved before users are aware of it.

In this year's Clear Choice VAT test, six vendors accepted our invitation, submitting seven tools. The vendors included Apparent Networks, ClearSight Networks, Empirix, Fluke Networks, Touchstone Technologies and WildPackets.

All products were tested in Miercom's lab using a detailed methodology to assess the tools in six categories (see How we tested VoIP analysis tools). The categories are configuration and deployment options, display and interface usability, traffic capture and real-time monitoring options (see story discussing the benefits of these data-gathering methods), diagnostics and trouble-shooting measures, and reporting capabilities and advanced features.

ClearSight's Analyzer garnered the Network World Clear Choice Award for its second year in a row. It topped our charts because of exceptional diagnostic tools and its advanced navigation and display features. Fluke's OptiView tool earned second place, showing strong in its real-time monitoring and reporting features. Here below is a product-by-product breakdown of how each tool fared when we plugged it in, turned it on and set it to watch our test network.