The five tools we reviewed dig deep into VoIP networks to root out the causes of problems and provide network administrators with easy-to-understand, graphical displays of VoIP activity.

In past reviews, we focused on the ability of these products to give network administrators insight into their company's VoIP networks. This time around, we wanted these products to help diagnose and repair the VoIP problems they see. Specifically, we looked for proof that they accurately isolate the problematic VoIP calls and facilitate for proactive management of VoIP streams.

Products from ClearSight Networks, Codima Technologies, JDS Uniphase (JDSU), WildPackets and Touchstone Technologies were tested by Miercom engineers in their central New Jersey lab. (For a full listing of available VoIP monitoring tools, see our Buyer's Guide.) 

Testing focused on six categories: setup, configuration and deployment; display and interface; real-time monitoring; diagnostics and troubleshooting; reporting, alerts and triggers; and advanced features. Some of those advanced features include extensive codec support beyond the G.711 or G.729/.729a that most analyzers support; Perceptual Evaluation of Speech Quality analysis for testing networks; R-factor correlation; the ability to measure video quality; special provisions for analyzing voice over Wi-Fi; and simultaneous multisegment analysis. 

All the products tested support Session Initiation Protocol (SIP) and can be used in multivendor VoIP environments. Codima's product did have a tighter integration for monitoring Avaya's VoIP line because Codima's first deployments were rooted in Avaya deployments. 

They differed primarily in how accurately they assessed the voice quality of degraded calls, how well they provided expert advice — the meaning of the error or logged event, suggestions on how to fix it, and what else to look for in the network related to the problem — and how many VoIP-specific alerts and other criteria they monitored. 

Most products could inject or replay traffic as well. Being able to replay the audio stream and hear for yourself what the suspected bad VoIP call sounded like offers a reality check to troubleshooting when it's coupled with mean opinion score (MOS) and R-factor scores. (MOS is a voice-quality rating that ranges from 1.0 [worst] to 5.0 [best].) As a side benefit, this feature allows you to apply traffic back on the network for limited stress testing, predeployment-site-survey purposes or other, more involved troubleshooting tests of the underlying network hardware in the converged network.