Enum has your number

If the Internet and the public telephone network are to converge — as most in the IT industry expect — there needs to be a simple and efficient way to reconcile their addressing schemes.

With the public switched telephone network (PSTN), the way to reach another telephone is by dialing its unique telephone number. To reach another computer device on the Internet, however, you must use the domain name system and the device's unique IP address.

Getting the two to meet is a critical job that might fall to a little-known standard called Enum, short for electronic numbering. Its low profile is not expected to last. Internet telephony is being sought by federal agencies and other large organizations that see many potential benefits in the technology, such as big cuts in long-distance phone bills.

Enum, developed last year by a working group of the Internet Engineering Task Force, is quickly gaining industry momentum. Several IP telephony vendors have announced plans to develop Enum-enabled products. And during the last several months, three companies have launched public pilot tests of Enum registries.

Any one of these registries could potentially develop into the foundation for a nationwide Enum infrastructure. That platform is considered a prerequisite for enabling the ultimate goal of computer-based telephony: the ability to make end-to-end phone calls using only regular data networks and avoiding the phone network entirely (see diagram).

"Enum standardizes the way in which you actually dial a phone number over the Internet without having to go to the PSTN for translation services" to an IP address, said David Fraley, principal analyst with Gartner Inc.'s Dataquest unit in San Jose, Calif. "Enum is a major step in helping to deliver voice-data convergence on an IP network."

That's the promise of Enum on a basic, though important, network plumbing level. From the users' perspective, Enum would let people give out a single telephone number, yet have it connect to multiple IP-enabled communications devices, such as their telephone, wireless phone, e-mail client, fax machine and wireless handheld computer.

"One thing Enum solves is the "business card' problem of too many addresses.... Over time you'll see people using a single telephone number as an address for a Web page or an e-mail address, or to receive a fax or an instant message," said Tom McGarry, chief of strategic technical initiatives at NeuStar Inc., Washington, D.C., one of three companies testing an Enum registry database.

The other companies running Enum test beds are VeriSign Inc., Mountain View, Calif., and NetNumber.com Inc., Lowell, Mass. Each of the test beds consists of a registry database into which other companies adding Enum capabilities to their products can register telephone numbers and associated IP addresses.

The other test-bed participants include large enterprises, telecommunications carriers, IP telephony vendors and network equipment manufacturers. They are testing to make sure that when their applications query the Enum database with a registered telephone number, they receive the associated IP addresses in response. VeriSign and NetNumber, which started their trials last winter, say there are now hundreds of companies participating in their trials. They expect Enum-enabled products to be available later this year.

All three test-bed operators believe that the full development of an Enum registry will be an important catalyst for the growth of the IP telephony market and provide greater benefits for organizations, such as federal agencies, that adopt the technology.

"Routing calls over the IP network instead of the PSTN will absolutely save agencies money," said Lori Whitted, vice president of marketing and business development at VeriSign's global registry division.

Although the companies report that the standard is working well from a technical perspective, much still needs to be resolved in terms of government oversight of the technology's deployment.

In the United States, the Commerce Department controls the Internet domain name system, while the Federal Communications Commission is responsible for telephone numbering. Enum, of course, touches both of these worlds.

Discussions about which agency will oversee Enum deployment are occurring within a study group at the State Department, which is involved by virtue of its role as the U.S. representative to the International Telecommunication Union. The ITU is responsible for the E.164 standard, which describes the format of telephone numbers used around the world and is the primary record in the Enum model for linking to other IP addresses.

"Oversight for Enum will probably end up with the FCC," said Glenn Marschel, chief executive officer of NetNumber.

Another issue to be resolved is whether more than one company can operate the main Enum registry database in the United States, to which all Enum queries will eventually be directed. All three test-bed operators are vying for the business.

VeriSign, through its Global Registry Services division, already provides Internet registry services for the .com, .net and .org domain names. And NeuStar has the sole U.S. government contract to operate the so-called local number portability database of all U.S. telephone numbers. For its part, NetNumber has built a service carrier-grade operation to host its Enum test bed, which is designed for 99.999 percent availability.