Rule No. 1: There Are No One-Stop Shops -- Network Managers Must Take The Time To Sort Out IP Telephony's Many Flavors
By Robert Harbison
September 7, 1999
At first glance, IP telephony seems like a great idea.
The basic transport is already a standard. IP is the
leading network protocol worldwide by a vast margin.
In addition, there's a worldwide network already in
existence in the form of the Internet, and virtually all
large enterprise networks can use IP, even if that's
not their primary protocol.
Unfortunately, it takes more than IP to make a
network. While the transport mechanism for IP
telephony may remain the same for all such means
of communication, the process to make it happen
can vary greatly. The result is that many types, or
flavors, of IP telephony exist and, for the most part,
they're incompatible.
Fortunately, standards are on the way. Still, there's
a great deal that needs to be done between the
standards that exist today and true universal
connectivity in the world of IP telephony.
For now, the choices companies make are
frequently dictated by what they already have. For
example, if a company wants to add VoIP to an
existing PBX installation, the choices are limited to
products that will work in that environment.
Likewise, to add VoIP support to an existing
enterprise network, the product must work with the
existing network infrastructure.
While there are products that are less dependent on
the existing environment than others, they in turn
have varying degrees of feature support and
flexibility. Because of these choices and limitations,
choosing the right flavor of IP telephony can have a
dramatic impact on how well an existing network will
support IP telephony and what the choices will be in
the future.
PBXs
Many PBX providers worldwide have now begun to
offer VoIP integration as an internal PBX option.
VoIP can save on communications costs by sending
the corporate voice call over an existing data
network, including the Internet. The voice/data
network card is tightly integrated within the PBX and
truly provides a network telephony solution, as long
as the terminating PBX is also capable and
integrated in a similar fashion.
There's an obvious problem. If an incompatible PBX
is at the other end of the call, then network
telephony won't work at that particular destination.
The PBX vendor's only option is to replace the
existing PBX with its own models.
An additional problem with PBX products is that the
router operating systems do not provide any
application programming interfaces (APIs) that will
allow the PBX to control the priority of router data
streams, and therefore quality of service (QoS)
guarantees cannot be provided.
Routers
Router vendors have become the new competitors to
the PBX vendors in the IP telephony market. These
vendors operate under the assumption that most
telephone calls will migrate to packet-based data
networks over the next decade.
The products offered by router vendors seem to be
primarily based on a " dumb pipe" technology that
can provide dial-tone and voice-over-net; but they
have severe limitations in the enhanced features and
management services they can provide.
In essence, router vendors have not created an API
that will let applications control or interact with the
voice communications channel and internal router
hardware. These APIs will be necessary to provide
any enhanced services or virtual PBX features that
can integrate with the collaborative computing
environment of desktop applications.
If the same vendor's products are implemented
throughout the network, the routers can provide QoS
guarantees by assigning higher priority for the voice
data streams, but it generally requires that the same
router model be installed at all locations.
Unfortunately, most enterprises do not have the
capability to completely replace the existing router
infrastructure with new equipment.
Stand-Alone Hardware
Numerous stand-alone hardware offerings provide
voice-over-net services for VoIP, voice-over-frame
relay and voice-over-ATM. Voice-enabled frame relay
access devices (FRADs) are the most common and
generally are very economically priced. Voice
FRADs are available from Micom, Motorola, Nuera,
Acclaim and many other vendors. Products in this
category vary in capability from two analog voice
connections up to multiple T1 connections that can
provide scalability for carrier-grade products.
These types of hardware products commonly offer
QoS guarantees through priority schemes that are
usually proprietary within their hardware and not
compatible with other manufacturers' products. If
these systems are implemented within corporate
networks where there is an existing router
infrastructure, the QoS priority is rendered ineffective
when the VFRAD is behind the primary router and
poses a firewall security problem if it is placed in
front of the primary router.
Gateways
Software voice gateways are available from a wide
variety of vendors and provide a diverse set of
services, including dumbpipe gateways, Web
callback gateways and even SS7 gateways that
integrate with the PSTN's signaling system.
Software gateways are usually based on off-the-shelf
hardware and are built on top of existing operating
systems, such as Unix, Sun and Windows NT. As
with PBX and hardware solutions, most software
gateway vendors can't provide QoS guarantees
because they can't control the priorities of the router
data streams.
New-Gen PBXs
The new generation of PC-PBXs and IP-PBXs offer
full-featured, low-cost PBX alternatives for small to
medium office environments consisting of user
stations for 10 to 250 users. Most of these systems
provide many enhanced PBX features: voice-mail
options, auto-attendant and Interactive Voice
Response functionality and VoIP transport services.
However, most of these vendors have no method for
integrating with the primary corporate office PBXs or
the services that they provide. This makes the small
PC-PBXs and IP-PBXs islands of sophisticated
communications services that are not integrated
with the corporate communications services. When
the enterprise has implemented a central voice-mail
system or other central PBX service, these systems
cannot be integrated.
Voice Application Integration
IP telephony is not just about cheaper telephone
calls; it is also about the delivery of new and
enhanced voice and data services, integration and
collaborative computing.
The integration of these combined voice and data
services offers a wide variety of features that include
sophisticated "follow-me" services, virtual PBX
features, guest office support, and mobility and
telecommuter support.
The key to these enhanced services is tight
integration with the PBX through computer telephony
integration (CTI) and with the data network
infrastructure through directory services integration
(DSI).
The combination of CTI and DSI provides the
necessary information and control of the telephony
and data networks that foster the creation of a new
breed of voice services. In essence, the voice gate-
way is transformed into a combination desktop CTI
server, a mobility server and an IP telephony
gateway server.
While the choices are limited at most companies,
there is still likely to be more than a single choice
that will work in the existing environment. Selecting
the appropriate choice can have significant long-term
effects on how a company approaches the future
and how it will deal with IP telephony as it evolves
over the next several years.
Most IT managers will find that the choices they
have range from easy to hard and cheap to
expensive. Getting your PBX vendor to add IP
telephony capabilities to an existing installation may
be easy, but it won't be cheap. Likewise,
implementing a new system that integrates
everything well and has the flexibility and
expandability needed for the future won't be easy or
cheap, but it could be the best long-term choice.
The only certainty is that the correct choice of
flavors will be unique to each company.
Copyright c 1999 CMP Media Inc.
<<INTERNETWEEK -- 09-06-99, p. PGI5>>
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