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Convergence: ENUM is a Big Deal

Convergence as a technology concept has been around for decades. Many have predicted the convergence of electronics and entertainment, of PC’s and TV’s, and more recently of WiFi and cellular. All of these areas are in fact undergoing various degrees of convergence but there is another area that many are not as familiar with. It is called ENUM. The Internet Engineering Task Force (IETF) issued a “request for comment” on ENUM (RFC 2916) in September 2000. Basically, ENUM is a protocol that will make it possible to converge the Public Switched Telephone Network (PSTN) and the Internet. In other words, a telephone number can get you to a Web service—telephone number in, URL out. The idea can be extremely useful when you consider that most telephones are limited to twelve keys on a keypad. Ever tried to enter your alphanumeric login ID and password to a web site on a cell phone or Personal Digital Assistant? It is next to impossible! The biggest impact of ENUM will probably be for Voice Over IP (VoIP). In fact, it could be the tipping point. ENUM is a really big deal.

The ENUM protocol takes a complete international telephone number and “resolves” it to a URL using a Domain Name System (DNS) architecture. DNS is what converts www.whatever.com into a numeric address that gets you to the whatever Web site. ENUM is sort of the reverse. The user puts a telephone numbers into the DNS and it gets converted to a url and thereby provides access to a wide range of applications—based solely on a phone number. The most exciting application is a streamlining of Voice over IP, in which telephone calls can be made over the Internet. Imagine keying in a fax machine number on your Personal Digital Assistant and a document from the PDA appearing on someone’s fax machine or a call to a Web service that locates someone and sends a message to their Instant Messaging program if they are on-line or to their email inbox if they are not. The possibilities are endless.

NeuStar, Inc., founded in 1996, is providing critical clearinghouse services to enable communications networks to interoperate (converge). They are hoping to become the industry’s trusted neutral third party. The heads of the Department of Commerce’s National Telecommunications and Information Administration (NTIA), the Federal Communications Commission (FCC), and the Department of State’s International Communications and Information Policy expressed their support this week for the idea of a private sector selection process to pick a company to begin o provide ENUM services. This could enable ENUM to move from a theoretical idea to the beginning of a very big and important thing.

Meanwhile, the International Telecommunication Union (ITU), which specifies the format, structure, and administrative hierarchy of telephone numbers, has come up with E.164 which is an international telephone numbering plan . This is what will be used in ENUM. A “fully qualified” E.164 number is designated by a country code, an area or city code, and a phone number.

For example, a fully qualified E.164 number for the phone number 555-1234 in Washington, DC (area code 202) in the United States (country code 1) would be +1-202-555-1234. That telephone number is then translated into an Internet address by removing the dashes and reversing the order of the digits. The domain “e164.arpa” is appended to the end and so the end result of the translation is Simple enough, right? ENUM then issues a query on and this in turn will lead to your bank or airline or whatever Web service is represented by the phone number. It might also lead to services which today go through traditional telephony networks including a voice conversation over the Internet.

The reason for the reversed phone numbers (right to left) and dots is that that is how DNS works. DNS was selected for use with ENUM because it’s already there, it’s works, it’s global, it scales, it’s fast, and it’s open. . When you type www.ibm.com the first step in finding the numeric address of IBM is to look at the .com domain, then to ibm, and then to the world wide web server. If you want to take a deep dive on DNS structuring, take a look here. Fortunately, the user will not have to do any of this manually. It will be done by the application (e.g., in the web browser) or device (e.g., an Internet-enabled telephone) that supports ENUM. The user simply dials a telephone number in the traditional manner.

There are many issues to be worked out and it will take time but the U.S. government putting it’s support behind the idea this week is an important step. We used to call to order something. Today we type www.buyitnow.com. Tomorrow we might be calling again—but this time to a web server!

By John R. Patrick, President of Attitude LLC

Worked at IBM for 35 years. VP of Internet Technology from 1995 to 2001. e-tired at end of 2001. Author of five books including Health Attitude: Unraveling and Solving the Complexities of Healthcare (2015). Founding member of W3C at MIT in 1994. Fellow of the IEEE. Member of board at Keeeb, Inc. and OCLC, Inc. Holds degrees in electrical engineering, management, law, and health administration. Website and blog at johnpatrick.com.

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Dustin  –  Oct 20, 2003 12:50 PM

I do not believe Enum will be all that useful with out an authentication system that validates the origin of calls. It’s all well and fine to be able to resolve the destination of a call across the Internet using the standard numbering plan. But the question will become should we accept a particular call from the Internet. This is a problem that has NOT been solved for email yet.

Hasani  –  Oct 21, 2003 12:38 PM

Authenticate against whom?  Have one single entity that controls your signon? All due respect to your comments, it’s highly inpractical.  With ENUM being so similar to DNS, how would you verify that all DNS queries are legit?  You can’t(yet).  But we all take it for granted that when we pick up the telephone to answer a call, that the caller id info is correct.  You are correct that this could be a problem, (spam anyone?) and no solution has been ratified for email.

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