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RFC 3026

Liaison to IETF/ISOC on ENUM

Pages: 6

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Network Working Group                                           R. Blane
Request for Comments: 3026                                           ITU
Category: Informational                                     January 2001

                      Liaison to IETF/ISOC on ENUM

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.


Working Party 1/2, of the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) held a meeting of its collaborators in Berlin Germany 19-26 October 2000. The agenda of the meeting contained several contributions regarding RFC 2916: "E.164 Number and DNS" from the Internet Engineering Task Force's (IETF) ENUM Working Group - more specifically, the method for administering and maintaining the E.164-based resources in the Domain Name System (DNS) as related to the ENUM protocol. Consequently, in addition to the WP1/2 collaborators, there were several members of the IETF present to assist with the discussion of issues contained in the aforementioned contributions. This liaison from WP1/2 to the IETF/ISOC conveys the understandings of the WP1/2 collaborators resulting from the discussions.

1. Considerations under Question 1/2 (Numbering)

Throughout this document, the terms "administration" or "administrative functions" refer to the provision and update of the E.164 numerical values, to be contained in the zones of a domain name in the "" domain, in the DNS. It is noted that most ENUM service and administrative decisions are national issues under the purview of ITU Member States, since most of the E.164 resources are utilized nationally. These understandings are relative only to the provision of E.164 information for DNS administrative functions, not policy or operational functions.
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   In order to advance a common terminology for the purpose of this
   liaison, we have defined the zones of a domain name as follows.

   Using an example, domain name "" (as
   in RFC 2916) is segmented into zones as follow: - domain zone

      3.3. - country code zone (1, 2, or 3 digits dependent on CC) - national zone

   The first understandings to be conveyed are those regarding the
   responsibilities for administration of the various zones within the
   "" domain:

   o  The domain zone administration was agreed to be outside the scope
      of this meeting and WP1/2.

   o  For all E.164 Country Code Zone resources (Country Codes and
      Identification Codes), the ITU has the responsibility to provide
      assignment information to DNS administrators, for performing the
      administrative function.  The ITU will ensure that each Member
      State has authorized the inclusion of their Country Code
      information for input to the DNS.  For resources that are spare or
      designated as test codes there will normally be no entry in the
      DNS.  However, the ITU will provide spare code lists to DNS
      administrators for purposes of clarification.  The entity to which
      E.164 test codes have been assigned will be responsible for
      providing any appropriate assignment information to DNS

   o  The administration of National Zone numbering information is
      determined by the type of Country Code resource that a National
      Zone is behind:

      *  The national zone, for geographic resources, is a national
         matter and is, therefore, administered by the ITU Member
         State(s) to which the country code is assigned.  In an
         integrated numbering plan, e.g., CC "1", each Country within
         the plan may administer their portion of the resource in a
         different manner.

      *  For national zone resources behind the Country Codes assigned
         to and shared by Networks, the entity to which the resource is
         assigned provides the E.164 assignment information, to DNS
         administrators for performing the administrative function.
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      *  For national zone resources behind the Country Codes assigned
         to and shared by Groups of Countries, the administrative entity
         identified by the Countries of the Group provides the E.164
         assignment information, to DNS administrators, for performing
         the administrative function.  Note that the creation of this
         category is dependent upon the approval of draft Recommendation

   o  Each of the administrative entities responsible for the
      administration of resources within the zones (as identified above)
      is individually and separately responsible for ensuring that DNS
      administrators are aware of appropriate changes to their resources
      once they have agreed to their input into the DNS.

   o  Assigned geographic E.164 resources, for all zones, not authorized
      for input by the appropriate administrative entity will not be
      entered into the DNS under any circumstance.  For example, if the
      ENUM service is not approved for use in a country, by the
      appropriate ITU Member States, the E.164 numbers of that country
      will not be input to the DNS.

   o  With regard to Number Portability, it was agreed that WP1/2 would
      further study this issue, in the context of ENUM.  However, it is
      currently understood that this study and its result will not
      impact the IETF and its work.

   o  The study being undertaken within WP1/2 (referred to above) will
      also attempt to identify options and provide guidance to assist
      those entities charged with the task of providing the
      administrative information to DNS administrators.

   o  All administrative entities, including DNS administrators, will
      adhere to all the applicable tenets of all pertinent ITU
      Recommendations, e.g., E.164, E.164.1, E.190, and E.195, with
      regard to the inclusion of the E.164 resource information in the

   o  The ITU, IETF, and IAB will jointly cooperate fully to ensure that
      the agreed administrative procedures to accommodate the above
      understandings, and any other mutually agreed appropriate future
      understandings, will be implemented and adhered to on an ongoing
      basis.  The ITU may request the consultation of the WP1/2 experts
      as necessary and as prescribed in Resolution 20.
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2. Additional items below are from Q.10/2 Rapporteur Group (Service Issues)

o The issues surrounding number portability are to be addressed in the draft supplement to Recommendation E.370 o This issue surrounding freephone service was expanded to include other global services (i.e., International Premium Rate Service and International Shared Cost Service). Preliminary findings would indicate that routing the call to the appropriate destination will depend on successfully receiving information about the geographic point of origination (e.g., calling "telephone Number"). A proxy server would process such information and either redirect or forward the call (based on the proxy owner's decision) on to the appropriate destination. o The issue surrounding selection of the IP gateway within a PSTN- to-IP call flow may depend on options that may be available to telephony carriers in such selection. The WP1/2 collaborators thank their IETF counterparts who attended this meeting and assisted in the resolution of these issues. Any questions regarding the contents of this liaison should be referred to the WP1/2 Chairman Roy Blane at

3. Security Considerations (added by the IESG)

The ENUM solution uses the Domain Name System (DNS) for storage of information. Delegation and distributed administration is done according to DNS routines. The E.164 numbers are though distributed according to a different algorithm than domain names. This Liaison Statement describes how mapping E.164 number administration and DNS administration can work together, and how further discussions are delegated to each administrative body for the country codes in E.164 space. If delegation and mapping is not done carefully between E.164 and DNS there is a risk of "napping" of E.164 numbers when they are stored in DNS. It is also important that the DNS strictly hierarchal system is preserved (see RFC 2826 [1]).

4. References

[1] IAB, "IAB Technical Comment on the Unique DNS Root", RFC 2826, May 2000.
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5. Author's Address

Roy Blane ITU EMail: URI:
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6. Full Copyright Statement

Copyright (C) The Internet Society (2001). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society.