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Versions: 00 01 draft-ietf-enum-infrastructure-enum-reqs

ENUM                                                             S. Lind
Internet-Draft                                                 AT&T Labs
Expires: April 22, 2006                                        P. Pfautz
                                                                    AT&T
                                                        October 18, 2005


                Carrier/Infrastrucure ENUM Requirements
                 draft-lind-infrastructure-enum-reqs-01

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document provides requirements for "infrastructure" or "carrier"
   ENUM, 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.




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Conventions used in this document

   RFC2119 [1] provides the interpretations for the key words "MUST",
   "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
   "RECOMMENDED", "MAY", and "OPTIONAL" found in this document.


1.  Infrastructure ENUM

1.1.  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 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.

   For purposes of this document, "Carrier of Record" refers to the
   entity that provides PSTN service for an E.164 number with the
   understanding that this definition is ultimately a matter for
   national authorities to determine.

1.2.  Background

   Carriers use E.164 numbers currently as their main naming and routing
   vehicle.  Carrier ENUM in e164.arpa or another publicly available
   tree allows Carriers to link Internet based resources such as URIs to
   E.164 numbers (Note: this is the other way round then User ENUM).
   This allows Carrier in addition to interconnecting via the PSTN (or
   exclusively) to peer via IP-based protocols.  Carriers may announce
   all E.164 numbers or number ranges they host, regardless if the final
   end-user device is on the Internet, on IP-based closed NGNs or on the
   PSTN, provided an access (e.g.  SBC or gateway) to the destination
   carriers network is available on the Internet.  There is also no
   guarantee that the originating carrier querying Carrier ENUM is able
   to access the ingress network element of the destination carriers
   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 carriers, resolving the final
   destination network within the shared network.


2.  Requirements for Infrastructure ENUM





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2.1.

   Infrastructure ENUM SHALL provide a means for a carrier to populate
   DNS RRs in a common publicly accessible namespace for the E.164
   numbering resources for which it is the carrier-of-record.

2.2.

   Queries of infrastructure ENUM FQDNs MUST return a result, even if
   the result is NXDOMAIN.  Queries must not be rejected, e.g. based on
   ACLs.

2.3.

   Infrastructure ENUM SHALL support RRs providing a URI that can
   identify a point of interconnection for delivery of communications
   addressed to the E.164 number.

2.4.

   Infrastructure ENUM SHALL support an IRIS capability that allows
   qualified parties to obtain information regarding the E.164 numbering
   resources and the corresponding carrier-of-record.

2.5.

   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 registrations.

2.6.

   Infrastructure ENUM SHALL be implemented under a TLD that can support
   reliability and performance suitable for PSTN applications.

2.7.

   Infrastructure ENUM MUST meet all reasonable privacy concerns about
   visibility of information an end user has no control over, for
   example discovery of unlisted numbers, or inadvertent disclosure of
   user identity.

2.8.

   Proposed implementations of Infrastructure ENUM SHOULD

   a.  Minimize changes required to existing requirements that are part
   of RFC 3761



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   b.  Work with open numbering plans

   c.  Restrict additional functionality to carrier resolvers.

   d.  Minimize the number of lookups required to obtain as many NAPTR
   records (end-user and carrier) 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.


3.  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 carrier ENUM.  Where the Tier 1 registry
   is able to identify the carrier 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 a carrier 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 carriers register all of the their
   allocated (as opposed to assigned) numbers.  Unassigned numbers
   should be provisioned to route to the carrier's network in the same
   fashion as assigned numbers and only then provide an indication that
   they are unassigned.  In that way, carrier registration of a number
   in ENUM provides no more information about status of a number than
   could be obtained by dialing it.


4.  IANA Considerations

   IANA considerations will depend on the architecture ultimately chosen
   to meet the requirements.

5.  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)



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        Application (ENUM)", RFC 3761, April 2004.

   [3]  International Telecommunications Union-T, "The International
        Public Telecommunication Number Plan", Recommendation E.164",
        May 1997.














































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Authors' Addresses

   Steven Lind
   AT&T Labs
   180 Park Ave
   Florham Park, NJ  07932-0971
   USA

   Email: slind@att.com


   Penn Pfautz
   AT&T
   200 S. Laurel Ave
   Middletown, NJ  07748
   USA

   Email: ppfautz@att.com

































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