Network congestion and lack of packet prioritization are hurting VOIP, according to Brix

July 31, 2006

3 Min Read
Study: VOIP Quality Getting Worse

A recent study has found the quality of VOIP calls declining steadily over the past two years, and points to network congestion and lack of service prioritization as the culprits. (See VOIP Quality Dropping.)

Brix Networks Inc. has come up with a clever way to study the quality of VOIP calls -- a portal called where consumers themselves place dummy calls. Brix says the site has generated nearly a million test calls since it launched in March 2004. (See Report Hisses at VOIP Quality.)Brix says almost 20 percent of those calls rated “unacceptable” against a long-used quality testing algorithm called the “E Model.”

“It’s pointing to congestion and competition with other media,” Brix CTO Kaynam Hedayat says of the study’s implications. “There’s no differentiation in the network between VOIP and other kinds of traffic like video or gaming -- it’s just pure democracy.”

The test calculates a Mean Opinion Score (MOS), a common objective measure of conversational voice quality that rates calls on a scale from one (bad) to five (excellent) based on such things as jitter, packet loss and latency. (See Keynote Monitors VOIP and Who Makes What: Test & Measurement Gear for Next-Generation Networks.)

Test calls with a MOS of 3.6 or better, Brix says, are typically regarded as having satisfactory quality. Only 81 percent of the test calls achieved the 3.6 threshold.

Some in the VOIP business feel such studies show that VOIP providers are victims of their own success. “You’re dealing with consumer expectations as much as you are changes in call quality,” says SunRocket Inc. spokesman Brian Lustig. “Consumer expectations of land-line service are very high, and as more consumers begin to feel comfortable with VOIP, expectations rise.” (See VOIP Testing Goes Live.)

Lustig disagrees that overall VOIP quality is on the decline. “There’s been an explosion of VOIP use in the last couple years, and part of the reason for that is VOIP quality has improved,” Lustig says. Indeed, the global market for consumer VOIP has grown to nearly 20 million subscribers, researchers say.

Lustig says call quality improvement is one of the main things driving VOIP providers toward forming peering arrangements with one another. (See VoicePulse Peers With XConnect.) VOIP providers can avoid the “uncertainty” of the PSTN by forming direct IP handshakes with other VOIP providers, Lustig says.

Global IP Sound AB CEO Gary Hermansen points out that when a voice call leaves the IP domain for the PSTN, it must be transcoded into a lower-quality sound stream. He says quality is further challenged by the fact that VOIP services are now used by millions of people, and by the fact that video packets have been added to the service in many cases. (See Skype Uses Logitech, On2.) displays a real-time “weather map” of the Internet's current ability to support real-time services, such as VOIP and IPTV. Registration is required to use the site.

Brix’s interest in the subject stems from its own product line -- real-time VOIP and IPTV testing and monitoring gear. Brix is one of a growing number of companies marketing the technology; others include:

  • Agilent Technologies Inc. (NYSE: A)

  • Anritsu Corp.

  • Apparent Networks

  • Empirix Inc.

  • InfoVista SA

  • JDSU (Nasdaq: JDSU; Toronto: JDU)

  • Minacom

  • Navtel Communications Inc.

  • Psytechnics Ltd.

  • QoSmetrics Inc.

  • QoVox Corp.

  • Radcom Ltd.

  • Spirent Communications

  • Sunrise Telecom Inc. (Nasdaq: SRTI)

  • Tektronix Inc.

  • Telchemy Inc.

(See Who Makes What: VOIP Infrastructure Equipment, VOIP Testing Goes Live, VOIP Testing: The Startup Mentality, and Empirix Upgrades VOIP Tracker.)

— Mark Sullivan, Reporter, Light Reading

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