The US government came out in favor of accelerating ENUM plans in February 2003, but little has happened since, as the telecommunications, cable and internet industries try to hammer out the details of how implementation should happen.
Interested parties organized into a group called the ENUM Forum have agreed that the best way to introduce ENUM in the US would be to form a limited liability corporation, which would receive contractual authority to run ENUM from the government.
But there is still disagreement over how the ENUM registries contracting with this LLC would be required to operate. The complex issue takes into account political boundaries and competition and revenue concerns.
ENUM maps phone numbers into domain names by reversing the order of the digits and putting dots between them .You then add .e164.arpa to the end. So the phone number +1 415 543 5496 becomes the domain name 6.9.4.5.3.4.5.5.1.4.1.e164.arpa.
E164.arpa has been designated by the Internet Engineering Task Force as the Tier 0 root of the ENUM tree, from which all subdirectories will take their cues. It is operated by RIPE-NCC, the body also responsible for IP addressing in Europe.
E.164 is an International Telecommunications Union standard way of organizing phone numbers by geography and delegating responsibility over those numbers to countries, so that no two phone numbers in the world are the same.
ENUM domains look complex and not particularly user-friendly, but end users will likely never see one. Rather, applications such as IP phones could use ENUM to look up the address of the endpoint they are trying to contact.
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The system is expected to be a crucial component of globally interoperable VoIP, but it is not limited to voice. ENUM could be used to address fax machines, pagers, modems, email clients, and text terminals for the hearing impaired, according to the IETF.
The idea is that nations apply to RIPE to be delegated the Tier 1 for their country code. The UK’s Department of Trade and Industry was given control over 4.4.e164.arpa back in 2002, for example. About 20 country codes have been delegated so far.
One of the problems with +1 is that it is one of only a few dialing codes that actually represent geographic areas larger than one nation. There are 19 countries under +1, including the US, Canada, and most of the Caribbean.
Virginia-based NeuStar Inc manages +1 under the North American Numbering Plan, and intends to bid to run the ENUM equivalent when the opportunity arises, according to NeuStar VP of strategic technology initiatives Tom McGarry.
One of the more interesting questions is of course how would we select an ENUM Tier 1 registry in the US, McGarry said. But we need to set it up in a way that ensures that these other countries can select their own Tier 1s.
Working out how to resolve the +1 problem has become a major talking point. The current thinking, according to NeuStar, is that a Tier 0.5 could be created that would delegate various more localized area codes to multiple Tier 1 registries.
In this scenario, the Tier 0.5 would be skinny, with a total registrant base comprised just of the 800 or so area codes (like 212 for New York and 415 for San Francisco) that appear under +1. The revenue would mostly flow to Tier 1 registries.
On the flipside of the revenue equation, there are concerns about how ENUM will affect existing cash cows, such as carriers’ directory businesses. But most people are agreed that technologically speaking, ENUM is already there.
With regards to ENUM, everyone thinks that is a solved problem, at least from a technology point of view, said Paul Mockapetris, who wrote the DNS spec in 1983 and is currently chairman and chief scientist of Nominum Inc.
Mockapetris said ENUM is just a part of the VoIP puzzle. Companies are currently working on many other interoperability specs that will help VoIP offer a similar level of functionality to regular telephony (such as call waiting, calls on hold, etc).
Meanwhile, Pulver.com Inc, which offers a PC-to-PC VoIP service called Free World Dialup, has applied to the Internet Corp for Assigned Names and Numbers for the right to launch a .tel top-level domain, which would use ENUM.
Pulver.com CEO Jeff Pulver recently told ComputerWire that .tel would be fully compatible with e164.arpa, despite the fact that critics and competitors have been saying it will interfere with the numbering plan.
Pulver blames NeuStar for working behind the scenes to shoot down its chances at being approved by ICANN in 2000, a charge NeuStar denies. But NeuStar does think .tel is a bad idea and will likely resist the application this time around too.
As the North American Numbering Authority, we think you can’t just give an entity that doesn’t have the oversight of a regulatory authority the ability to put telephone numbers in the public space like that, McGarry said.
Mockapetris said he had not read Pulver’s .tel application, and declined to comment, but said his understanding was that a TLD is essential for their marketechture, but not essential for their architecture.
This article is based on material originally published by ComputerWire
