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June 1997
By David Greenfield
Internet Telephony
IP Telephony Gateways: Long Distance With a Local Touch
Placing calls over the 'Net will make for big savings----so get the goods on the gateways now
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Act now and save. It may sound like the dubious tag line to too many late-night TV ads, but when it comes to Internet
telephony gateways, getting off the dime really does mean holding on to the dollars.
That's because net managers can use this new crop of products to
redirect voice traffic over the Internet or corporate intranet--which
means no bills at all for some long-distance calls and just local
charges for others. What's more, everything takes place transparently:
Users simply pick up their phones and dial--and there's no noticeable
drop in quality.
There's another reason to move fast: The market is just taking
shape. Many vendors won't be shipping product until later this year,
which means net managers can get a jump on the facts now--and learn
what makes certain gateways stand out. Begin by assessing the
architecture: Some vendors use digital signal processing technology,
which makes these products more scalable than their CPU-based
counterparts. Then check the types of messages each gateway can
handle, whether it's voice, video, fax, or a combination. Finally,
keep an eye on the price: If it looks s
uspiciously low, the vendor is
probably selling software and interface cards only--and not a complete
system.
Networkers who get their homework out of the way can then get ready
to enjoy the benefits. Take Michael Gleissner, a partner at online
bookseller ABC Bücherdienst GmbH (Regensburg, Germany). Unable to
find qualified workers for an overnight help desk in Germany, he's
setting one up in Florida instead--with plans to redirect customer
calls to it over the 'Net via the Internet Telephony Server from
Lucent Technologies Inc. (Murray Hill, N.J.).
"Routing calls across the Internet was an economical solution that
wouldn't have been possible using regular international circuits,"
Gleissner says. "And based on early testing of Lucent's product, our
customers shouldn't notice a change in voice quality."
Players and Payoffs
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BUILD YOUR OWN CUSTOM TABLE
A Selection of Internet Telephony Gateways
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What Gleissner's comments don't reveal is that Lucent is a PBX
vendor and isn't shipping its gateway until September--facts that only
serve to illustrate the newness of the market. Need more evidence?
Small players like Phonet Communications Ltd. (Herzlia, Israel) and
Vienna Systems Corp. (Kanata, Ontario) are holding their own against
giants like Micom Communications Corp. (Simi Valley, Calif.), while IP
telephony gear leaders Netspeak Corp. (Boca Raton, Fla.) and Vocaltec
Ltd. (Herzlia) also are in the picture.
Then there are established videoconferencing and fax gateway
vendors like Netxchange Communications Ltd. (San Francisco) and
RADvision Ltd. (Tel Aviv, Israel), which are adapting current products
to handle voice over IP. Waiting in the wings is Computer Protocol
(Malaysia) Sdn. Bhd. (Kuala Lumpur, Malaysia), whos
e CpIP Voice
Gateway is expected to win FCC approval in August and European
attachment approval by October. (Two gateway vendors--Ericsson Telecom
AB [Stockholm, Sweden] and Micro Call Ltd. [Ra'anana, Israel]--are not
included in this profile. At the moment, Ericcson sells its Internet
telephony gateway to carriers only, while Micro Call's doesn't permit
users to place calls from a phone.)
But just because the market isn't quite defined doesn't mean net
managers should hang back and wait. After all, Internet telephony
gateways represent a whole new way of doing things. With voice traffic
traveling over the IP network, there's no bill at all for
long-distance calls between company sites. Long-distance calls made
outside the company are shunted to the local PSTN (public switched
telephone network) at the other end of the link.
That may sound simple--but to understand how it all happens it
helps to look at the technology. Start with the gateways themselves,
which consist of three parts: codec sof
tware that typically runs on a
dedicated PC and handles the packetization, compression, decompression
of voice calls; line interfaces for the PSTN (public switched
telephone network) or PBX and network interface cards for the LAN; and
software that takes care of session management and intergateway
communications.
By masquerading as a PBX, the gateway emulates a typical phone
network. When a user dials a number, a call setup message is sent to
the PBX. It then sends a setup message to the local gateway. This
gateway then consults a table to locate the IP address of the remote
gateway. The two gateways establish a session, and the one on the
receiving end requests its PBX to complete the call. The phone rings,
and the recipient picks up.
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Gateways to Savings
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As the phone begins to ring, the origin
ating gateway runs the
incoming voice traffic through the codec and sends these packets
across the intranet or Internet to the receiving gateway. The
receiving gateway reverses the process, resequences and decompresses
the packets, and retransmits them to the recipient (see
Figure 1
).
Smooth Scaling?
But before net managers put the gateway into use, they may want to
make sure it's up to the demands of the enterprise. Architecture is
the issue here: Find out if the gateway's codec software runs on the
dedicated PC's processor, or if it runs on a plug-in DSP (digital
signal processor) board.
Simply put, gateways that run on the processor are much less
scalable. Although such products use third-party line interface cards
to put the incoming PSTN signal onto the PC's bus, the codec algorithm
still runs on the processor. And that can quickly become a bottleneck,
since every call on every port has to go through its own, separate
cycle of compr
ession and decompression.
The Telephony Gateway from Vocaltec manages to handle 12
simultaneous calls--but it does so with the help of the D/240SC-T1
board from Dialogic Corp. (Parsippany, N.J.). And even then, 12 calls
is the absolute maximum: Because the board is designed for
unidirectional use, each session requires 2 channels of a 24-channel
T1 (1.544-Mbit/s) line.
Is there a benefit at all to CPU-based gateways? Yes--time to
market. Writing compression/ decompression algorithms for DSP
platforms is a time-consuming task. In fact, it's so much of a hassle
that Vocaltec decided not to take advantage of the DSPs embedded in
the D/240SC-T1 board, according to Ravi Gururaj, Internet telephony
marketing manager at Dialogic.
Regardless, the move to DSP architecture is inevitable: All vendors
have it in their plans. And there are those gateways that already use
DSPs--like the T1 version of Netspeak's Webphone Gateway Exchange,
which can handle 24 simultaneous calls. Vienna's Vienna.way us
es
proprietary cards to scale to 48 ISDN BRIs (basic rate interfaces) or
96 digital connections.
With its V/IP, Micom takes a slightly different approach. The
vendor offers a DSP board with two analog lines that it says can be
added to a PC without severely affecting performance. But the amount
of connections the V/IP can handle is limited by the number of slots
in the PC.
By year's end, gateway vendors should be able to boost capacity
higher. Dialogic is now developing a board that has its own processor,
in addition to DSPs and line interfaces. That means it can run
everything but the high-level management software. "The upshot is that
with these kinds of cards, you can scale up to 96 or so lines without
resorting to proprietary cards," says Bibi Rosenbach, vice president
of research and development at Netxchange.
Get the Messages
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MESSAGE SERVER
Join the discussion about Internet Telephony
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As the Internet telephony gateway market begins to take shape,
products that handle voice alone may have a hard time keeping up.
That's because many vendors have multimedia in their plans--and are
developing gateways that pass not just voice but also fax, data, and
video between circuit- and packet-switched networks.
Faxing lends itself particularly well to this technology, since
faxes aren't delay-sensitive. In other words, quality is never an
issue--and net managers still stand to gain the same benefits in terms
of money saved.
Every gateway vendor but Phonet and RADvision offers fax
capability. (On the other hand, RADvision is alone in offering
videoconferencing support.) A few vendors use LCR (least-cost routing)
technology for sending faxes across the 'Net: The gateway can
determine the cheap
est path for getting a fax to its recipient. Among
these is Netxchange--whose Internet Xchange will use LCR to handle
voice as well, perhaps by this fall, according to president and
general manager Israel Drori.
And as the technology evolves, networkers can equip users with
multimedia PCs and dialer software for placing calls across the
Internet to other IP-attached users, or to another gateway. What's the
payoff? A PC might have icons for setting up such functions as
call-transfer and call-conferencing--which is much easier than
punching it out on a telephone keypad. And, of course, the PC has it
all over the phone when it comes to videoconferencing.
What's more, an IP telephony network can over time be tailored to
handle additional services--like the ability to place a phone call
from a Web page. MCI Communications Corp. (Washington, D.C.) and
Sprint Corp. (Kansas City, Mo.), for instance, have developed
technology that lets Web visitors set up voice calls simply by
clicking on an icon.
Some vendors aim to dispense with telephone systems altogether,
replacing phones with multimedia PCs. A LAN-based PBX would then take
on all of the call-management, accounting, and billing software found
in a traditional PBX today.
Companies that don't go in for an entirely new network might
instead want to try what Vocaltec calls a CMA (Call Management Agent)
server. CMA permits users to configure a profile for how and where
they can be contacted--and by whom. "I might configure my profile to
put all calls through to my work line from 8 a.m. to 11 a.m., route
calls to my voice mail until 4 p.m., and forward all calls afterwards
to my cellular phone," explains Ido Ganor, director of product
management at Vocaltec.
Ports: Your Call
After sorting through these issues, net managers can turn their
attention to price. This is where they really need to keep their wits
about them, because costing out an IP telephony gateway can be
tricky.
Why? Every vendor uses a per-port pricin
g scheme--but "port" can
have a variety of definitions. Most vendors use the word to refer to
the logical connection, not the physical interface. Thus a T1 with its
24 channels contains 24 ports, an ISDN interface with its 2 B channels
consists of 2 ports, and an analog interface contains 1 port.
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CONTACT AUTHOR
dgreenfield@data.com
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Then it comes down to determining what's included in that per-port
price. Netexchange and Vocaltec, for example, furnish gateway software
alone (for $1,200 and $1,350 per port, respectively). But corporate
networkers will have to purchase a dedicated PC ($2,000), operating
system software ($400), network adapters ($200), and line interfaces
($300 to $600 per port) separately. However, Micom, Netspeak, and
Phonet furnish line interfaces as well--and their prices a
re
noticeably lower.
Lucent, RADvision, and Vienna are the only vendors to offer
complete systems. That means their per-port pricing is pretty
low--although the cost of entry tends to be high. For instance,
Vienna's per-port pricing of $2,000 works out to a $16,000 overall
cost when applied to an eight-port gateway. Although the vendor offers
per-port pricing as low as $1,200, it's only for configurations of 96
ports or more--which drives the cost for a complete system past the
$100,000 mark. In contrast, RADvision uses proprietary architecture
and prices its four-port L2W-323 at $1,000 per port.
David Greenfield is international technology editor at Data Communications International and is based in Jerusalem. He can be reached at
dgreenfield@data.com
.
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