2.7.18 Telephone Number Mapping (enum)

NOTE: This charter is a snapshot of the 47th IETF Meeting in Adelaide, Australia. It may now be out-of-date. Last Modified: 03-Feb-00


Scott Petrack <scott.petrack@metatel.com>

Transport Area Director(s):

Scott Bradner <sob@harvard.edu>
Vern Paxson <vern@aciri.org>

Transport Area Advisor:

Vern Paxson <vern@aciri.org>

Mailing Lists:

General Discussion:enum@ietf.org
To Subscribe: enum-request@ietf.org
In Body: subscribe
Archive: ftp://ftp.ietf.org/ietf-mail-archive/enum/

Description of Working Group:

This working group will define a DNS-based architecture and protocols for mapping a telephone number to a set of attributes (e.g. URLs) which can be used to contact a resource associated with that number.


Telephone numbers now identify many different types of end terminals, supporting many different services and protocols. Telephone numbers are used to identify ordinary phones, fax machines, pagers, data modems, email clients, text terminals for the hearing impaired, etc.

A prospective caller may wish to discover which services and protocols are supported by the terminal named by a given telephone number. The caller may also require more information than just the telephone number to communicate with the terminal.

As an example, certain telephones can receive short email messages. The telephone number is not enough information to be able to send email; the sender must have more information (equivalent to the information in a mailto: URL).

From the callee's perspective, the owner of the telephone number or device may wish to control the information which prospective callers may receive.

The architecture must allow for different service providers competing openly to furnish the directory information required by clients to reach the desired telephone numbers.

Working Group Goals and Scope:

The working group will specify a DNS-based architecture and protocols which fulfill at least the following requirements:

1. The system must enable resolving input telephone numbers into a set of URLs which represent different ways to start communication with a device associated to the input phone number.

2. The system must scale to handle quantities of telephone numbers and queries comparable to current PSTN usage. It is highly desireable that the system respond to queries with speed comparable to current PSTN queries, including in the case of a query failure.

3. The system must have some means to insert the information needed to answer queries into the servers via the Internet. The source of this information may be individual owners of telephone numbers (or the devices associated to the number), or it may be service providers which own servers that can answer service-specific queries. The system shall not preclude the insertion of information by competing service providers (in such a way which allows for the source of the information to be authenticated).

4. The system shall enable the authorization of requests and of updates.

5. The Working Group will carefully consider and document the security and performance requirements for the proposed system and its use.

6. The Working Group will understand the impact of developments in the area of local number portability on the proposed system.

The Working Group will take into consideration how number resolution using the ENUM system is affected by the PSTN infrastructure for telephone numbering plans, such as the ITU-T E.164 standard.

The area directors will consider chartering an additional working group to pursue a non-DNS-based approach, if there's a constituency for the approach and a viable charter.


1. ENUM shall not develop any protocols or system for routing calls of a specific service or for locating gateways to a specific service. One example of such a service is mobile telephony, and one example of such gateways is IP telephony gateways.

2. ENUM shall not develop protocols for the "intelligent" resolution of these queries. That is, the updates to the ENUM data are limited to the insertion, update, and removal of URL information, and will not include inserting "logic" into the servers (to be used to respond to queries in an "intelligent" manner). (Of course, servers are free to support such intelligent services, but the insertion of such logic is not the object of ENUM standardization).

Document deliverables:

1. Telephone Number to IP Mapping Service Requirements (Informational)

2. Telephone Number to IP Mapping Service Architecture and Protocols (Standards Track)

These documents will specify the architecture and protocols (query, update) of the ENUM system.

3. A MIB for managing the service

4. The Working Group may decide to deliver a document which describes the relation between ENUM and E.164 or other PSTN telephone number infrastructure.

Goals and Milestones:

Nov 99


Initial draft of Service ENUM Requirements

Jan 00


Initial draft of ENUM Protocol

Mar 00


Revised draft of ENUM Service Requirements

Mar 00


Revised draft of ENUM Protocol

Mar 00


Possible draft on relation between ENUM and E.164 or other PSTN infrastructure

May 00


Initial draft of ENUM protocol MIB.

Jul 00


Submit ENUM Requirements document to IESG for publication as Informational

Jul 00


Submit ENUM Protocol document to IESG for publication as Proposed

Jul 00


Possibly submit ENUM relation with E.164 / other PSTN document

Sep 00


Submit MIB document to IESG for publication as Proposed


No Request For Comments

Current Meeting Report

None received.


None received.