VoDSL -- fine for today, not for tomorrow
last column, we tried on Voice over DSL (VoDSL) for size. We concluded that VoDSL
could prove advantageous, if provided with broadband data services.
For the longer term, however, what SOHOs and small businesses are really looking for
is a way to bring digitized and compressed voice and video directly from the premises
to large voice-ready IP backbones without moving through any legacy
According to DSL Reports, one of several
valuable DSL information sites on the Internet, my ideal case scenario -- packetized
voice as well as data -- can be built, but is not currently a commercially viable
There are two commercially deployable forms of VoDSL. A VoDSL provider can run voice
on a DSL connection straight to a voice/data gateway in the central office, at which
point the digital signal is sent to any voice switch for standard voice transmission
over the long distance network of my choice. Alternatively, the voice packets can go to
a digital subscriber line access multiplexer (DSLAM) where they merge with packets from
other DSL lines, which in turn are all sent to the voice switch. At the DSLAM, the
Internet (data only) connection usually goes to an IP carrier's backbone.
The primary reason that carriers don't offer packetized voice over DSL today is not,
in fact, the prohibitively high cost of the local broadband access, but rather two
other simple reasons. First, the quality of service we have on voice circuits today
cannot be guaranteed when voice packets are mixed with data traffic; second, the
supplementary services customers have grown accustomed to (and can have with VoDSL),
such as voice messaging, call waiting, and caller ID, are not supported in today's
commercial VoIP infrastructure.
I suspect that VoDSL, like other emerging communication services, will be an
important way for service providers to differentiate themselves in the next two to
three years, but within five years it won't make business sense for many operations.
When data network access costs are higher than voice access costs, VoDSL will not be a
significant value add. At that time, my vote would be to switch again. Those averse to
technology risks should stay with POTS and only sign up for more robust, 100-percent
VoIP service when available.
Bottom line: small offices, like businesses with thousands of employees, need VoIP
service to bypass local providers for voice and data, and to connect them directly with
a lower-cost VoIP network for long-distance calls. They won't find a long-term solution