Last week some VOIP services were described as alternative means of communication over
the regular telephone. However, VOIP is not a magical service that can immediately
replace your regular telephone. No matter how good the marketing strategy of the VOIP
provider is about their service, the voice quality is still highly dependent on the
Internet connection of the calling party and the called party.

Regular telephone calls, even international calls, have superb voice quality and this is
expected because normal telephone service, technically called PSTN or public switched
telephone network have dedicated voice channels for each caller. This means that there
is no other data traffic that could cause issues with the voice quality. However,
callers using cheap phone cards for international calls are really not using the usual
PSTN network but they bypass the normal international links to avoid the high cost of
international long distance calls. These callers normally experience very long delays in
hearing the other party.

VOIP calls, on the other hand, use the Internet to route the voice traffic to the other
caller using protocols called SIP, H323 or other proprietary protocols like what Skype is
using. VOIP therefore competes with other Internet use like browsing, email, downloads
and games. VOIP requires only about 25kbps to 80kbps of bandwidth depending on protocol
and codec used. Broadband Internet access services normally have specifications of
384kbps to 2MBPS but users should keep in mind these services are shared with many users
so these numbers are the maximum you can get if you are lucky. And since there is no
committed information rate or CIR, it is hard to say how much bandwidth you really get.
Most other Internet applications try to use all the bandwidth they can get so if doing
VOIP calls, avoid doing downloads, otherwise, the voice quality will be very poor. Even
if VOIP requires a relatively small bandwidth, this bandwidth must not be shared with
other applications. In short, VOIP needs a small but dedicated bandwidth.

Most residential users may find that VOIP call quality, while not near like normal PSTN
call quality, is good enough for their use. They might also find that certain times of
the day will have good voice quality while at other times, the calls are very choppy. As
long as the Internet service providers do not give dedicated bandwidth to subscribers,
VOIP call quality will vary. But at the end of the day, the cost savings of VOIP and the
possibility of unlimited talk time is appealing and certainly is a good compromise to
varying call quality. Just make sure that both ends of the VOIP call are not using their
Internet service for other applications like downloads, to increase the chance of good
voice quality during the call.

Next week, we will go into other technical details that affect VOIP service.