U.S. Study Group A Ad Hoc on
Steven D. Lind
2, Room 2G25
Florham Park, NJ 07932
US Implementation of ENUM
contribution has been prepared by AT&T to assist the SG-A Ad Hoc in
and it should not to be considered a binding proposal on
or any of its representatives.
reserves the right to change, amend or withdraw this
at any time.
US Implementation of ENUM
Authoritative Public Root
providers need a verifiable root for ENUM translations in order to offer
carrier-class services. While other roots are being offered within several
test-bed environments, AT&T continues to have concerns, as discussed
below, about the viability of multiple roots within a commercial-service
environment. AT&T believes that the Study Group A Ad Hoc should
concentrate its activities on issues that result in the rapid
implementation of an authoritative public root (or “golden tree”).
AT&T also believes that the United States should also adopt this
position within the ITU.
A major concern centers
around the possibility that different customer data may be stored in each
of several different roots for the same E.164 telephone number. The
results of such a situation may prove chaotic and yield unpredictable
results. It is not clear that
proposed ENUM-specific DNS resolver software could handle multiple roots
to extract correct, unambiguous customer records.
The problem is akin to today’s directory assistance services
provided by multiple suppliers, in which a number of databases contain
records for the same customer, however in many cases the records are wrong
and inconsistent between databases.
Top Level Domain
AT&T prefers the use of
“.arpa” as the top-level domain (TLD) for ENUM implementation. While
other TLDs have been discussed for an authoritative public root, none of
them, including “.int,” satisfy any of the issues raised by the French
at the last meeting of Study Group 2 (see Delayed Contribution 15).
The “.arpa” TLD is best suited for the implementation of ENUM
“.arpa” is an infrastructure domain.
“.arpa” is furthest from ICANN involvement. “.int” is
currently controlled by ICANN, a situation that is unlikely to change in
the near future, if ever.
The ITU will be in control over what data goes into the
“e164.arpa” domain. While this would also be true for most alternative
TLDs (obviously not for private commercial trees such as “e164.com”),
it negates the argument that a different TLD is needed to place the ITU in
control of the domain.
“.arpa” provides additional operational and security
capabilities that are not accommodated by other TLDs. For example,
multiple highly distributed servers that do not fate share are deployed
around the world for the ".arpa" TLD, which ensures better
performance and reliability than for other TLDs, such as ".int".
The redundancy of this TLD is just one such feature from which ENUM
It is possible for multiple
parties to participate within a US authoritative tree, yielding some level
of “competition.” At the extreme, a separate Tier 1 Registry could be
established for each existing NPA. This
approach would allow easy separation of US ENUM implementation from
other North American countries. The Study Group A Ad Hoc Group on ENUM
should establish and recommend eligibility criteria that interested
parties would need to meet in order to participate as a Tier 1 Registry.
With such criteria established, a bid and award process should be
established through the US Government (or by some designated organization)
for each segment of the US authoritative tree at Tier 1.
interested in having U.S. ENUM service could form a Limited Liability
Corporation (as was done for the implementation of Local Number
Portability) to contract for the Tier 1 functionality. In this case, the
U.S. government should certify this entity as the U.S.
"e164.arpa" Tier 1 to the ITU.
All interested and
qualified parties should be able to provide Tier 2 services to end-users.
Many telephony, internet and application service providers will be
interested in providing ENUM services. Many of these providers will be
interested in providing services through the use of their own name servers
to minimize the cost of maintaining the end-users’ data within the NAPTR
records. For this reason, AT&T does not support the use of a Registry/Registrar model
in use today for other internet domains. The Study Group A Ad Hoc Group
should establish and recommend eligibility criteria for the provision of
services using these Tier 2 name servers.
In addition, there are many
issues, such as validating the end users’ intentions in establishing
ENUM services for a specific E.164 telephone number, and tracking of the
disconnect of an active E.164 number that require specification.
AT&T believes that for validations and disconnection of E.164
numbers, the parties that have information on number assignments, usually
the telephone service providers, should be involved. Methods for
inter-entity exchange of information, including transfer of service
provider and notification of termination of service were developed for the
implementation of local number portability, and some of these techniques
may be applicable to ENUM administration as well.
Some of the processes used for Local Number Portability along with domain
registration should be examined to develop ENUM administration procedures.
Part of this process should include the telephony service provider
for an E.164 number notifying the Tier 1entity when the user relinquishes
service on the number.
AT&T feels that
specific criteria should be established for reliability, security and
performance of the ENUM services. In
particular, minimum acceptable performance requirements, such as, “the
ENUM service should perform, in all respects, at least as well as DNS
performs today,” should be established.
Guidance should also be provided as to how the reliability,
security, and performance objectives will be monitored and enforced.
With wide availability of a
number of Tier 2 entities, competition at the Tier 2 level will ensure
responsiveness to the needs of end users.
model is used for some domains within the Internet, particularly
".com." In this model, a single primary name server exists at
the top-level domain that is managed by a single entity. Other entities
act as registrars by interfacing with end-users, collecting desired domain
names from the end users and updating the registry on the end user's
For example, if I wanted to
register the domain name "sdlind.com" I could use Yahoo as a
registrar. They would collect the necessary information to register the
desired domain name and a fee, taking care of all the necessary work
interfacing with the domain name server. Yahoo has no name server itself,
but has satisfied all the criteria imposed by the registry operator to
have update permission.