By Carolyn Duffy Marsan
Network World, 09/24/01
Money for nothing and calls for free. To paraphrase the English
rock band Dire Straits, that's what corporate network managers want in these
fiscally lean times.
Many companies have made major investments in Internet-based
backbone networks, and they're looking for ways to leverage those investments.
One way to ring up savings is to run internal voice and fax communications
over these already-purchased IP networks. But to make voice-over-IP applications
work, companies need some kind of a translation mechanism between the public
switched telephone network (PSTN) and the Internet.
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Enter Enum, a simple but powerful protocol that's generating
a great deal of interest among telecom carriers and Internet players. Enum
lets an end user type a telephone number into a Web browser and access a URL
listing the available Internet resources for that number, such as an IP telephony
address, e-mail address and Web address.
As vendors roll out support for the protocol in devices such
as Internet-enabled PBXs and telephones, and service providers build in the
required directories and other infrastructure, Enum will enable a much-needed
service for initiating telephone calls over the Internet. Enum also offers
the promise of providing a single point of contact for multiple communications
devices, from phones to PCs to fax machines.
"The most significant interest in Enum is for IP telephony,"
says Tony Rutkowski, vice president of Internet strategy at VeriSign of Mountain
View, Calif., which plans to introduce private Enum services for corporations
later this year.
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Enum evolution
The Internet Engineering Task Force finalized the Enum specification
about a year ago, and the first Enum products and services are due out this
fall. Among the companies that helped develop Enum were Cisco, Lucent, Nortel
and AT&T.
Enum is expected to roll out in the corporate market first.
Companies that run their own telephone systems will be able to map their employees'
telephone numbers to a private Enum service that points to corresponding IP
telephony addresses, e-mail addresses, fax numbers and cell phone numbers.
These companies can use Enum to direct internal telephone calls to their IP
backbone networks, which will cut the cost of long-distance calls between
branch offices.
"For really large enterprises with multiple call servers,
they can use Enum internally to cut down costs," says Jim Pilgrim, an engineer
with Alcatel tracking Enum's development in the standards bodies. "But
for most companies, the real savings will come from external phone calling"
between companies over the Internet, Pilgrim says.
These savings won't materialize until Enum is available on the Internet and a critical mass of corporate users evolves (see Enum's ROI.) And that
could take years because policy makers are still debating how
to introduce Enum into the Internet's DNS.
Telephone
numbers are highly regulated, with each country having sovereignty
over the assignment of numbers within its country code. At issue
is whether countries also will have authority over Enum registrations
and how best to support competitive but interoperable Enum services.
Most telephony and Internet companies favor a single, global
top-level domain for Enum services dubbed "Tier 0." Each country
would have a central Tier 1 registry that operates underneath the Enum top-level
domain. Service providers would offer corporate Enum registration services
at the Tier 2 level.
A handful of companies, including VeriSign, support the idea
of multiple top-level domains for Enum services.
The International Telecommunication Union (ITU), which oversees
telephone numbering on a global basis, is meeting this month to discuss its
Enum strategy. Vendors say they hope consensus will emerge on how the ITU
will move forward with a public Enum service.
"It's going to take a long time for a global, public Enum
service to be available," predicts Doug Ranalli, founder and chief strategy
officer at start-up NetNumber of Lowell, Mass., which was the first company
to offer Enum registrations. "But the enterprise space can move forward
independent of that process. . . As enterprises move forward with converged
network platforms, that represents an opportunity for Enum."
Three U.S. companies, NetNumber, VeriSign and NeuStar,
the North American telephone numbering authority, are running
Enum test beds. These test beds have attracted several hundred
participants, including software and hardware developers and service
providers.
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Questions to ask Enum service providers.
How often do you update your Enum directory?
What fees do you charge for Enum registrations, additions, deletions and changes?
What security mechanism does your Enum directory support?
What protections do you offer against outsiders spamming your Enum directory?
How are you designing your private Enum services to accommodate uncertainty about how a public Enum service will evolve?
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The first Enum products are likely to be Internet-enabled
telephones, PBXs and call managers. These products will be aimed at corporations
rolling out private Enum services in conjunction with voice-over-IP applications.
"We are working with the equipment vendors to build our
Enum service right into their applications, so when a service provider sells
to a customer, [the customer's] address is populated in our Enum directory
automatically," Ranalli says. "How you provision the directory and how
you query the directory have to be embedded in the application."
Two gray areas for Enum are security and performance. IP telephony
services need to be as secure and as fast as today's telephone services,
vendors say.
"We take for granted when we make a telephone call that
the caller is me and that no one else is listening in unless they have a search
warrant," says Lori Whitted, vice president of business development for
VeriSign Global Registry Services in Dulles, Va.
To achieve that, Enum service providers will need streamlined
security mechanisms for checking the authentication of telephone numbers as
well as speedy resolution. Hence, authentication vendor VeriSign's interest
in the protocol. Rutkowski adds that some ideas for multitiered public Enum
implementations would result in seconds-long delays and resolutions that are
too slow for Internet users.
"We think there's an opportunity to make Enum more secure
and faster than the technology that's here today," he says.
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Enum meets SIP
Most Enum proponents predict the technology's initial use
will be alongside another emerging IP telephony technology called Session
Initiation Protocol (SIP). SIP is a signaling protocol used to establish Internet
telephone calls, multimedia conferences, chat sessions and interactive communications.
"We think Enum is going to point to a SIP address and then
an IP address," Rutkowski says.
The first SIP trials were held this summer. Most of the vendors
announcing plans to support Enum already offer SIP.
Enum's ROI
Cheap and easy is the pitch.
Enum is not expected to add significantly to the cost of IP telephony products, with it likely being deployed as a software upgrade.
"With voice over IP, the whole value proposition is that you save money at the end of the day," says Lori Whitted, vice president of business development for VeriSign Global Registry Services of Dulles, Va. "It may be that your IP PBX costs a little more with Enum, but you should be getting a return on that investment."
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Columbia University in New York is one of the first organizations
to test how well SIP and Enum work together. So far, results are encouraging,
says Henning Schulzrinne, associate professor of computer science.
Columbia is running a SIP test bed that supports voice communications,
multimedia conferencing and unified messaging for 12 employees in its computer
science department. Columbia added Enum support last spring using software
from NetNumber. Enum handles the mapping between the telephone numbers active
on the SIP test bed and the SIP URL used to handle calls.
Enum helps during the transition period from a traditional
to an IP PBX, when some users are on each, Schulzrinne says. "You'd use
Enum as the central database to keep track of whether a person has a traditional
PBX number, in which case no translation is required, or a SIP URL that you'd
use to route the call to an IP phone locally or off campus," he says.
He also sees a role for Enum in helping companies forward
telephone calls for employees who move from one site to another.
"There's a way to do that by performing some PBX magic,
but it's much easier with Enum," Schulzrinne says.
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Outstanding issues
Although efforts such as the Columbia test indicate Enum technology
is stable, vendors are trying to clarify implementation issues. One such issue
is how Enum records, which show what Internet services are available for a
particular telephone number, will be administered in the Internet.
"How do competing service providers provision Enum records
into and out of an Enum database in a way that they trust each other?" asks
Matt Wald, vice president of IP services at NeuStar of Washington, D.C.
Enum administration issues likewise need to be hashed out
before services are introduced on the Internet.
NeuStar wants the U.S. government or an industry group to
host a competitive procurement to select a Tier 1 Enum administrator for the
U.S., and NeuStar hopes to win that procurement. The Tier 1 administrator
would handle Enum transactions between service providers, while the service
providers would offer Tier 2 registration services to U.S. companies.
Wald predicts the U.S. will have a public Enum Tier 1 central
registry by the second half of next year.
From the enterprise perspective, all the application and service
information will be held by the Tier 2 service provider.
"Tier 2 is where the action is. . . That's where AT&T's
interest lies," says Steven Lind, standards strategy manager
for internation
al and IP numbering with AT&T Labs of Florham Park, N.J. AT&T
is banking that most large companies would prefer to outsource
Tier 2 Enum registrations.
Although these issues must be resolved for Enum to become
the transparent megadirectory its proponents claim it will be, its progress
is promising.
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