ENUM S. Lind
Internet-Draft AT&T Labs
Intended status: Informational P. Pfautz
Expires: February 9, 2007 AT&T
August 8, 2006
Infrastrucure ENUM Requirements
draft-ietf-enum-infrastructure-enum-reqs-03
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Copyright (C) The Internet Society (2006).
Abstract
This document provides requirements for "infrastructure" or "carrier"
ENUM (E.164 Number Mapping), defined as the use of RFC 3761
technology to facilitate interconnection of networks for E.164 number
addressed services, in particular but not restricted to VoIP (Voice
over IP.)
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Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Infrastructure ENUM . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Background . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Requirements for Infrastructure ENUM . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
6. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . . . 7
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1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC2119 [1].
2. Infrastructure ENUM
2.1. Definition
Infrastructure ENUM is defined as the use of the technology in
RFC3761 [2] by the carrier-of-record for a specific E.164 number [3]
to map a telephone number into a URI [4] that identifies a specific
point of interconnection to that service provider's network that
could enable the originating party to establish communication with
the associated terminating party. It is separate from any URIs that
the end-user, who registers their E.164 number, may wish to associate
with that E.164 number.
Infrastructure ENUM is distinguished from user ENUM, defined in
RFC3761 [2], in which the entity or person having the right-to-use a
number has the sole discretion about the content of the associated
domain and thus the zone content. From a domain registration
perspective, the end user number assignee is thus the registrant.
Within the infrastructure ENUM namespace, we use the term "carrier-
of-record" for the entity having discretion over the domain and zone
content and acting as the registrant. The "carrier-of-record" is:
o The Service Provider to which the E.164 number was allocated for
end user assignment, whether by the National Regulatory Authority
(NRA) or the International Telecommunication Union (ITU), for
instance a code under "International Networks" (+882) or "Universal
Personal Telecommunications (UPT)" (+878) or,
o if the number is ported, the service provider to which the number
was ported, or
o where numbers are assigned directly to end users, the service
provider that the end user number assignee has chosen to provide a
Public Switched Telephone Network/Public Land Mobile Network (PSTN/
PLMN) point-of-interconnect for the number
It is understood that the definition of carrier-of-record within a
given jurisdiction is subject to modification by national
authorities.
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2.2. Background
Voice service providers use E.164 numbers currently as their main
naming and routing vehicle. Infrastructure ENUM in e164.arpa or
another publicly available tree allows service providers to link
Internet based resources such as URIs to E.164 numbers. This allows
service providers in addition to interconnecting via the PSTN/PLMN
(or exclusively) to peer via IP-based protocols. Service providers
may announce all E.164 numbers or number ranges they host, regardless
of whether the final end-user device is on the Internet, on IP-based
open or closed Next Generation Networks (NGNs) or on the PSTN or
PLMN, provided an access point of some type to the destination
service provider's network is available on the Internet. There is
also no guarantee that the originating service provider querying
infrastructure ENUM is able to access the ingress network element of
the destination provider's network. Additional peering and
accounting agreements requiring authentication may be necessary. The
access provided may also be to a shared network of a group of
providers, resolving the final destination network within the shared
network.
3. Requirements for Infrastructure ENUM
1. Infrastructure ENUM SHALL provide a means for a provider to
populate DNS resource records (RRs) for the E.164 numbering
resources for which it is the carrier-of-record in a single
common publicly accessible namespace. The single common
namespace ultimately designated may or may not be the same as
that designated for user ENUM (e164.arpa.) The FQDN in the
resulting resource records will not necessarily belong to or
identify the carrier-of-record.
2. Queries of infrastructure ENUM fully qualified domain names MUST
return a result, even if the result is a Name Error (RCODE = 3).
Queries must not be rejected, e.g., based on access control
lists.
3. Infrastructure ENUM SHALL support RRs providing a URI that can
identify a point of interconnection for delivery to the carrier-
of-record of communications addressed to the E.164 number.
4. Infrastructure ENUM SHOULD be able to support an IRIS [5]
capability that allows qualified parties to obtain information
regarding the E.164 numbering resources and the corresponding
carrier-of-record. Determination of what information, if any,
shall be available to which parties for geographic numbers is a
national matter.
5. Implementation of Infrastructure ENUM MUST NOT restrict the
ability of an end-user, in a competitive environment, to choose a
Registrar and/or Tier 2 name server provider for end-user ENUM
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registrations.
6. Infrastructure ENUM SHALL be implemented under a top level domain
that can support reliability and performance suitable for PSTN/
PLMN applications.
7. Infrastructure ENUM MUST meet all reasonable privacy concerns
about visibility of information an end user has no control over.
It should, for example, support mechanisms to prevent discovery
of unlisted numbers by comparison of ENUM registrations against
directory listings, or inadvertent disclosure of user identity.
8. Proposed implementations of Infrastructure ENUM SHOULD:
A. Minimize changes required to existing requirements that are
part of RFC 3761
B. Work with open as well as closed numbering plans
C. Restrict the need for any additional resolver functionality
to service provider resolvers.
D. Minimize the number of lookups required to obtain as many
NAPTR (Naming Authority Pointer) records (end-user and
infrastructure) as possible.
E. Minimize the client knowledge of the numbering plan required.
F. Maximize synergies with end-user ENUM
G. Support interworking with private ENUM trees.(In this context
a private ENUM tree is one that is not under e164.arpa or
whatever namespace is chosen for infrastructure ENUM but uses
instead a privately held domain.)
4. Security Considerations
Existing security considerations for ENUM detailed in [2] still
apply. Note that some registration validation issues concerning end
user ENUM may not apply to infrastructure ENUM. Where the Tier 1
registry is able to identify the provider serving a number e.g.,
based on industry data for number block assignments and number
portability, registration might be more easily automated and a
separate registrar not required.
Some parties have expressed concern that an infrastructure ENUM could
compromise end user privacy by making it possible for others to
identify unlisted or unpublished numbers based on their registration
in ENUM. This can be avoided if providers register all of the their
allocated (as opposed to assigned) numbers. Unassigned numbers
should be provisioned to route to the provider's network in the same
fashion as assigned numbers and only then provide an indication that
they are unassigned. In that way, provider registration of a number
in ENUM provides no more information about status of a number than
could be obtained by dialing it.
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5. IANA Considerations
This document includes no actions to be taken by IANA. The
architecture ultimately chosen to meet the requirements may require
IANA actions.
6. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Faltstrom, P. and M. Mealling, "The E.164 to Uniform Resource
Identifiers (URI) Dynamic Delegation Discovery System (DDDS)
Application (ENUM)", RFC 3761, April 2004.
[3] International Telecommunication Union-Telecommunication
Standardization Sector, "The International Public
Telecommunication Numbering Plan", Recommendation E.164",
February 2005.
[4] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,
January 2005.
[5] Newton, A. and M. Sanz, "IRIS: The Internet Registry Information
Service (IRIS) Core Protocol", RFC 3981, January 2005.
Authors' Addresses
Steven Lind
AT&T Labs
180 Park Ave
Florham Park, NJ 07932-0971
USA
Email: sdlind@att.com
Penn Pfautz
AT&T
200 S. Laurel Ave
Middletown, NJ 07748
USA
Email: ppfautz@att.com
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