Voice Over Vonage - Page 2

By Gerry Blackwell
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Pluses and Minuses
Sending voice over the public Internet has an upside and some potential downsides.

On the upside, voice over Internet services are transportable. You can carry the voice gateway with you to another location, plug it into another high-speed Internet service — in a hotel or branch office — and make and take calls as if you were in your office.

This is because the voice gateway is identified on the network not by the telephone number but by its IP address — a unique four-part sequence of digits.

The downsides of voice over Internet all relate to connection quality and reliability.

The system sends the voice packets — discrete blocks of data — over the Internet from your office to the nearest point of presence (POP defined) of the voice over Internet service provider. In the case of Vonage, in most places in the U.S. this is not far.

At this first service provider POP, the conversation is switched on to a managed backbone network and sent to the POP nearest the destination point.

If the destination is a regular phone on the public switched telephone network (define), a gateway at the POP converts the signal and switches it to the phone network. If it's another Vonage phone, the call goes back on to the public Internet and stays as IP packets until it gets to the other party's voice gateway.

Whatever the receiving device — a voice gateway at a Vonage POP or a voice gateway at another subscriber's location — it must reassemble the packets received in order and convert them to analog, all in real time.

If packets arrive consistently late because they're held up by congestion on the Internet, even if it's less than a second, the voice will be delayed. This is called latency and makes normal conversation awkward, though not impossible.

The delay is similar in effect to what you experience talking on a satellite phone, though rarely as pronounced — or like overseas calls in the old days.

If voice packets are completely lost, which can happen, the voice may be garbled — jitter — or the person at the other end may experience clipping, tiny bits of sounds chopped off.

VoIP is by now a mainstay of corporate telecommunications, but in enterprise VoIP applications — either local area or wide area — the calls go over managed networks that can ensure that voice packets always get priority, virtually eliminating latency and jitter.

This is the downside of using the public Internet — there is no way to ensure voice packets get priority while they're on the Net. They're as subject to delays as any other Internet traffic.

Our Overall Experience
In most calls using the Vonage service — and we made many, including overseas calls — latency, jitter and clipping were not a factor. Volume levels were consistently higher than with calls on our telco line and voices often sounded clearer, though not as natural.

On a small minority of calls — usually the longer-haul calls — we experienced some very slight latency. We also noticed some jitter when the parties talked over each other. In a normal telephone call, you can usually make out what the other person is saying in these situations. With the poorer Vonage calls, the other voice was garbled.

On a very few overseas calls, Vonage could not connect to numbers reachable on a telco line. With Vonage, we received a fast busy signal. Later the same numbers worked fine on Vonage.

Whether this was due to problems with Vonage POPs, the PSTN long distance network Vonage uses or the telco at the other end was not clear. In any case, the percentage of calls on which there were problems was very small.

Do some cost comparisons — Vonage versus your existing telecommunications services. The pay-back for applications involving overseas calling in particular can be huge.

If the dollars make sense, experiment with voice over Internet — without taking out your regular phone lines. If the Vonage service isn't good enough for your small business, you can always go back to what you had.

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Based in London, Canada, Gerry Blackwell has been writing about information technology and telecommunications for a variety of print and online publications since the 1980's. Just for fun, he also authors features and columns on digital photography for Here's How, a spiffy new Canadian consumer technology magazine. Blackwells knowledge is vast and his wit eduring.

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This article was originally published on March 24, 2004
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