Telchemy's approach to VoIP QoS

Last time, we introduced the importance of real-time quality-of-service (QoS) monitoring in voice-over-IP (VoIP) networks. This time, we'll look specifically at Telchemy's method of providing VoIP QoS.

In a typical VoIP environment, the delay bounds for VoIP jitter buffers are set to levels designed to produce high call quality. Packets arriving outside the delay bounds are discarded and effectively "lost." And since traditional monitoring techniques don't effectively reflect packet loss due to the jitter buffers, they can end up understating the degradation in call quality.

Exacerbating the problem is the fact that the jitter buffer packet loss is usually accompanied by additional packet loss due to network congestion. By some estimates, up to 50% of packet loss in IP networks is caused by congestion when large packets burst beyond the network's capacity to manage the packet size.

Since packet loss can be introduced by jitter buffer delay management and by network congestion caused by large packets, QoS management must account for both types of loss, individually and in combination, Massad says.

Telchemy's answer is to ensure monitoring of both types of packet loss in real time.

According to Telchemy, its VQmon technology can monitor for packets lost in isolation and those lost in bursts. VQmon, as described in the European Telecommunications Standards Institute document TS 101329-5, correlates traffic statistics by time and against each other to provide a complete and accurate view of call quality in real time. This data can then be fed to QoS managers and controllers to allow for appropriate corrective action in real time, potentially pre-empting premature termination of VoIP calls due to poor quality.

Telchemy has one approach to solving the VoIP QoS management issue. Next time, we'll take a look at another.

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

WorldCom set for VoIP push
Network World, 02/04/02

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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