Should you be jittery about voice over the Internet?
 
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We were a little cruel in the way we ended the last newsletter. In the true spirit of a Buck Rogers serial, we left you hanging by simply stating that if the packets experiencing maximum jitter over the Internet were occurring in bursts, you had a problem. So this time, we'll talk about taking this analysis a step further.
Some of you may remember that a few months ago we had a rather lengthy discussion of jitter and its impact. For review, you might want to take a look in the newsletter archives at:
www.nwfusion.com/newsletters/converg/2002/01560825.html
www.nwfusion.com/newsletters/converg/2002/01573913.html
We said then that jitter is one of the most significant parameters, if not the most significant parameter, when it comes to measuring voice quality. And " bad " jitter reveals itself in jitter buffer discards that occur when packets that do not arrive soon enough are dropped rather than forwarded.
An analogy for jitter buffer discards: You missed the plane, and you don't get to stand by. You just go back home and don't take the trip.
In particular, the quality of a voice call can be predicted rather accurately by analyzing the nature of these discards, especially looking at the burstiness.
The good news is that there are tools for doing this analysis. For instance, Telchemy has software that can be imbedded into both network monitoring devices and endpoint devices for analyzing the burstiness of these discards on an extremely granular basis, down to discards within tens of packets. This gives the raw information to evaluate the relatively minor impact of occasional losses as compared with the major impact of bursts of lost packets. Consequently, the impact of jitter on voice quality can be very accurately assessed.
The bad news is that we can't say today whether the jitter on the Internet is low enough on an ISP-by-ISP basis to provide excellent voice quality. But the tools are available, and any ISP who is trying to sell you VoIP over the Internet should have these tools available as well.
RELATED LINKS
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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