VoIP requires full-time QoS monitors

We closed last year with a discussion about the various quality-of-service protocols for Ethernet and IP, including Multi-protocol Label Switching. This week, we'll look at how one vendor, Telchemy, proposes to add QoS to VoIP calls.

According to Robert Massad, vice president of marketing at Telchemy, QoS is more important for VoIP than for data-based applications because:

* VoIP is a real-time application.

* VoIP is human-sense-oriented and dependent on the user experience of call clarity.

* VoIP is more heavily affected by the variable time delays that exist in packet-based networks than is traditional data.

The variable delays in IP networks create variable call clarity. Since the delivery and receipt rate of voice communications wander up and down during the course of a session, network operators must monitor and correct the real-time quality of all calls to meet QoS commitments, according to Telchemy.

Telchemy and others, then, believe that QoS monitoring for VoIP can only be done successfully with a relevant data set from a real-time monitor running 24-7-365, rather than the more traditional look at isolated batches of statistics.

Massad notes that " if packet loss is high on a particular route, an 'overlay' may intercept the packet and reroute it. The problem is that these statistics are not only isolated and discrete, but are averaged or just absolute counts. Moreover, they do not distinguish between packet loss that is benign and packet loss that is destructive. "

VoIP managers traditionally attend to jitter, delay and packet loss. " The problem is that while these factors may affect transport service quality, in general, they have very little relation to call quality, " Massad says. " This is because VoIP end points have jitter buffers and codecs or voice coders, which remove jitter but add delay. "

Next time, we'll look at what happens when delay and packet loss are introduced in a VoIP call.

QoS at the IP layer, Part 1
Network World Convergence Newsletter, 11/26/01

MPLS and QoS, Part 1
Network World Convergence Newsletter, 12/10/01

Steve Taylor is President of Distributed Networking Associates and Publisher/Editor-in-Chief of Webtorials.Com. For more detailed information on most of the topics discussed in this newsletter, connect to Webtorials.Com, the first Web site dedicated exclusively to market studies and technology tutorials in the Broadband Packet areas of Frame Relay, ATM, and IP.

Larry Hettick is an independent consultant, with 19 years of experience in telecommunications and data communications marketing and product management for service providers and equipment vendors. He can be reached at larry@larryhettick.com

You can reach the authors at taylor@webtorials.com or larry@larryhettick.com.

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