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New tools quantify VoIP call quality

Management applications measure packet loss, jitter and latency to zero in on problems plaguing converged networks.

By Susan Breidenbach, Network World
March 28, 2005 12:01 AM ET
VoIP special report

Network World - Do you trust a computer to tell you how your CEO's new IP phone sounds?

Network testing and monitoring vendors are betting you will as they peddle new call quality management applications that pinpoint problems on converged networks. Despite increasing reliance on e-mail, voice remains executives' method of choice for closing deals, and businesses embracing VoIP can't afford to make assumptions about call quality.


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Clear Choice Test: VoIP analysis tools


Vendors such as Apparent Networks, Brix Networks, Empirix, Integrated Research, Qovia and Spirent are rushing to fill the void, often licensing algorithms for active testing and passive monitoring from call quality pioneers Psytechnics and Telchemy. "This is the beginning of a big push, though the standards for VoIP call quality measurement are still evolving," says Eric Siegel, senior analyst at Burton Group.

Frost & Sullivan reckons the emergent VoIP monitoring/management market hit $50.7 million in 2004, and expects it to increase about sixfold by 2008. IP telephony is exploding, and upfront network assessments will only take a VoIP implementation so far. Unlike data, it has to work perfectly out of the gate.

"VoIP can be made to run as well and as reliably and as clearly as the best traditional phone network, but it's not a static environment," says Pierce Reid, vice president of marketing for Qovia, a 3-year-old start-up dedicated to VoIP call quality. "It has entropy. This can be accelerated by the employee who decides to download 'Shrek 2' at lunchtime."

Keeping the canaries singing

Network professionals with converged environments liken IP telephony to the cages of canaries that used to accompany the miners below ground. The birds keeled over when conditions in the mine became unsafe. Voice is revealing network problems that used to go unnoticed on IP networks, and the standard data fix - more bandwidth - doesn't work.

"These real-time applications are showing us we have problems on the network end to end," says Walt Magnussen, director of telecom at Texas A&M University in College Station, which uses Apparent's AppareNet Voice software probe to support VoIP and video links to remote locations. "This new tool shows you where it is and what it is."

VoIP call quality management includes active and passive approaches, and particular products can encompass both. The active or intrusive approach is exemplified by British Telecom spinoff Psytechnics with its algorithms derived from years of subjective voice-quality testing. The method includes installing a thin client on various endpoints - such as phones, gateways and call servers - to take local readings and return a Perceptual Evaluation of Speech Quality metric.

"You insert a reference signal at one point, measure it at the destination, and through the use of algorithms calculate what the Mean Opinion Score would be," says George Hamilton, senior research analyst at The Yankee Group. "It's an active test, and it's more accurate." MOS is a metric of how good a voice call sounds (see story ).

This intrusive method allows for very targeted testing of specific network links and elements. The measurement goes end to end and establishes a baseline for comparison. Among the weaknesses, the simulated traffic eats up network bandwidth. Also, intrusive testing can be difficult when you don't control the entire path from one end to the other.

Telchemy championed a passive, non-intrusive approach that produces voice quality metrics extrapolated entirely from network statistics such as packet loss and jitter. The company's VQmon technology has been embedded in a range of third-party IP phones, gateways, probes, analyzers, switches and routers to enable real-time monitoring of VoIP call quality.

AppareNet Voice has been described as a hybrid of the non-intrusive and active approaches. The product generates test traffic and then uses software probes to listen to it, but doesn't require the installation of appliances or software agents at the remote sites.

"You just need to know the IP address at the other end, and you can do hundreds of sites an hour," says Gary Audin, president of Delphi, a network integrator in Arlington, Va. "Once you have to start putting agents in all the remote locations, it's a much bigger undertaking."

The remote locations in Texas A&M's VoIP network include extension facilities and experimental agricultural sites in Latin America, Africa and the Middle East. To help serve such areas, the university, an official Internet2 Technology Evaluation Center, also is working with the American Distance Education Consortium (ADEC) at the University of Nebraska and satellite provider Tachyon Networks on the prioritization of VoIP traffic over satellite links.

Texas A&M recently used AppareNet Voice to assess the voice capability of a link with an agricultural research center in Kenya, which starts with a terrestrial gateway connecting the U.S. and Europe and then moves onto a satellite link for the rest of the trip. The tool pinpointed a software problem in the infrastructure of the satellite provider, which could not come up with a cost-effective fix, forcing Texas A&M to look for an alternate carrier.

However, the university had better luck with the ADEC trials testing a path involving a satellite link out of San Diego, serving locations in Latin America. AppareNet Voice found a problem with a router, Tachyon replaced it, and the connection now supports VoIP.

AppareNet Voice sends out several hundred packets of various types to each router along the way and then uses the returning information to characterize the link and assess any problems.

"With this kind of tool, I can look into another carrier's network in a fairly non-intrusive fashion, without installing any software anywhere else," Magnussen says. "It's hard evidence for the vendor or service provider. The measurements aren't precise, but heck, for something you can come up with on demand in 4 or 5 minutes - it's pretty good."

Others feel the value of local appliances or agents throughout the network is worth the upfront time and expense. Apptis, a large network integrator in Chantilly, Va., uses the Qovia VoIP Monitoring and Management System internally and in VoIP implementations for clients.

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