I have spoken lately with people who seem to think an IP-PBX is LAN
telephony. I typically take a deep breath, and then launch into a harangue
explaining what I think LAN telephony is all about. I don't like equating
the IP-PBX with LAN telephony, since it narrows the thought process to just
the customer premise equipment (CPE) switching aspect. LAN telephony is
broader. It's all about the applications.
If you're one of those people with whom I've had this conversation,
there's no need to read on; you've heard it all before. But if you haven't
already heard my spiel, please allow me to explain.
"WHAT'S YOUR DEFINITION OF LAN TELEPHONY, JIM?"
First, you probably want to know just what my definition of LAN
telephony is. The first widespread LAN telephony application was the
enterprise gateway, which connected the customer's traditional PBX with an
existing LAN. The customer used the same PBX and phonesets as always, but
the infrastructure carrying the phone call was now the company intranet
instead of a circuit-switched carrier. These applications also allowed calls
to be made outside the intranet to a gateway outside the firewall -- most
likely a gateway that was part of a next-gen telco.
The next logical step beyond the gateway is the IP-PBX. For example, 3Com
has made large market strides in the past year with its NBX. The IP-PBX is
currently the part of LAN telephony that garners much media attention -- and
the reason I believe why many people equate LAN telephony with IP-PBX. So,
to me, the IP-PBX is the CPE switching done entirely over a LAN using IP
phones and IP infrastructure. There are no traditional telephony interfaces
beyond maybe a single analog trunk for emergency purposes.
But in our ideal converged world (which hasn't yet "converged"
with real life), installing a PBX with no traditional telephony interfaces
is a leap of faith some businesses are not yet ready to make. IS departments
have enough headaches -- "Leave me alone," they say. (And not just
when I call.)
To fill the gap, a very important product has emerged. IP-enabled PBXs
are hybrid time division multiplex (TDM) and IP-PBX products that give
businesses the option of combining traditional PBX functionality with LAN
telephony. They give an IS department the freedom to experiment with IP
phones in a controlled environment, then to move forward at its own level of
comfort. I'm seeing increasing interest in this type of environment, for it
gives the business the ability to start with a fully traditional setup, then
move to IP as they see fit. They can also start as a fully IP environment,
then go back to TDM if they need to. Either way, the organization preserves
its investment, since the flexibility is always there. Artisoft's
TeleVantage is an example of this type of PBX.
"WHAT ABOUT THE APPS?"
What about the apps, you ask? LAN telephony can be about serving
applications over IP to IP-PBXs -- what I refer to here as a media adjunct.
Have you ever called someone at a large company and reached an interactive
voice response (IVR) system, automated attendant, or speech dialed, and been
able to hear yourself being switched around? You're being passed to a media
adjunct server connected to the PBX over some sort of PBX integration
hardware or software. Since that same task can be accomplished over the LAN,
I consider this application to be as large a part of LAN telephony as any
IP-PBX. This is a great way for IP-PBXs to add applications to support their
Once the applications and the PBX are all on the same infrastructure,
true unified messaging is much easier. Think about all the applications that
are part of the LAN. There are e-mail servers, database servers, and Web
servers. When these are all part of the same switching infrastructure,
moving voice mails to e-mail, moving faxes to e-mail, storing e-mail in a
customer relationship management (CRM) database, or speaking real-time to
someone browsing your Web site all become much easier. We'll start seeing
these applications during 2001.
"WHAT DOES THE "LAN" INCLUDE?"
Since I'm on a roll, I have one more point to make about LAN telephony.
You may be asking just what the LAN includes. Do its boundaries stop at the
campus? At the firewall? I am so glad you asked.
Under any normal definition, the LAN is ballooning: Think about telecom
hosting -- using a telephony application server provider (ASP) to host
business applications. Both switching and the media adjunct applications can
physically reside off the customer's premise. Yet functionally, they serve
the CPE. Is this LAN telephony? Of course it is.
So there it is -- my view of LAN telephony. Whether you agree or disagree
on the fine points, we can all agree that LAN telephony is much more than
just an IP-PBX. And the definition is expanding daily. I do have passionate
feelings on this topic. So next time we meet in person, be sure to tell me
you've read this column. That way you won't have to listen to my harangue
Jim Machi is director, product management, CT Server and IPT Products,
for Dialogic Corporation (an Intel
company). Dialogic is a leading manufacturer of high-performance,
standards-based computer telephony components. Dialogic products are used in
fax, data, voice recognition, speech synthesis, and call center management
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