The VoIP management challenge

The slowly maturing VoIP platform has enterprises taking a long look at this technology, and not just for cost savings. Many of these potential users are opting for in-house rather than service-provider solutions because of the additional savings, future flexibility, and a simple lack of consistent vision by the large telco providers.

Those adventurous souls who implement VoIP themselves face the daunting task of managing a voice-oriented data network. For network managers accustomed to data networks, this job requires a specialized toolkit.

To determine the best option for the enterprise market, we gathered four VoIP testing contenders and turned them loose on the VoIP installations at our Advanced Network Computing Laboratory (ANCL) testing facility at the University of Hawaii.

The reviews below aren't intended as direct comparisons. These testing tools are different enough in their approaches to the VoIP management problem that an apples-to-apples comparison is simply unworkable. For this reason, we instead examined each tool on its own merits and rated them from the perspective of a typical network manager.

Acterna DA-3400 Data Network Analyzer

We reviewed the network testing capabilities of Acterna's product line in our March roundup. This time around, Acterna brought a DA-3400 equipped with its latest VoIP testing software technology. Heavily aimed at service providers and carrier-style implementations, the Acterna solution is feature-rich but probably overkill for all but the largest enterprise VoIP implementations.

As before, the DA-3400 comprises an innocuous, 1U rack-mountable box, which we attached to our network via a Net Optics tap. That's important, because unlike the Brix product, the DA-3400 is an entirely passive device.

To access the DA-3400's PVA-1000 VoIP analyzing software, you log into the box using a Web browser. We plugged the DA-3400 into our lab network and decided to expand its testing scope to reflect its carrier orientation. We skipped managing local VoIP traffic and instead aimed the device at an Asterisk SIP server used by Priority Networks.

We initiated several conversations using Priority's network and the same people in each conversation to preserve audio frequency ranges. We measured call quality during a series of two-minute conversations and captured both sides of the conversation so that we could play it back later.

To measure QoS and Diffserv, the DA-3400 displays the appropriate priority bits that tell the receiver (or router) what priority the traffic has. The big differentiator in Diffserv is that the priority labels must be correctly configured in order for the switch to "differentiate" the data streams.

Although Diffserv is mostly standardized by now, the standards continue to be implemented differently enough across platforms that having the ability to dig down to the bit level with the DA-3400 can be critical to fast problem resolution.