Network Working Group                                       F. Ellermann
Internet-Draft                                                     xyzzy
Obsoletes:  2606                                             D. Eastlake
(if approved)                                       Eastlake Enterprises
Intended status:  BCP                                    August 18, 2008
Expires:  February 19, 2009

                      Reserved Top Level DNS Names

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   The list of current Internet-Drafts can be accessed at

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   This Internet-Draft will expire on February 19, 2009.


   To reduce the likelihood of conflict and confusion, a few top level
   domain names are reserved for use in private testing, as examples in
   documentation, and the like.  In addition, a few second level domain
   names reserved for use as examples are documented.  This memo
   replaces RFC 2606 reserving 21 additional TLDs.

Editorial note

   This note and Appendix B should be removed before publication.  The
   draft can be discussed on the IETF Discussion <> mailing

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  TLDs for Testing, & Documentation Examples . . . . . . . . . .  3
     2.1.  ".example", ".tld" . . . . . . . . . . . . . . . . . . . .  4
     2.2.  ".invalid" . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.3.  ".localhost" . . . . . . . . . . . . . . . . . . . . . . .  4
     2.4.  ".test"  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Reserved Example Second Level Domain Names . . . . . . . . . .  4
   4.  Internationalization Considerations  . . . . . . . . . . . . .  5
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  5
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  6
   7.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  6
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     8.1.  Normative References . . . . . . . . . . . . . . . . . . .  7
     8.2.  Informative References . . . . . . . . . . . . . . . . . .  7
   Appendix A.  Educational Info  . . . . . . . . . . . . . . . . . .  8
   Appendix B.  Document History  . . . . . . . . . . . . . . . . . .  9
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
   Intellectual Property and Copyright Statements . . . . . . . . . . 13

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1.  Introduction

   The global Internet Domain Name System is documented in [RFC1034],
   [RFC1035], [RFC1123], [RFC1591], [RFC3696], and numerous additional
   Requests for Comments.  It defines a tree of names starting with
   root, ".", immediately below which are top level domain names such as
   ".com" and ".us".  Below top level domain names there are normally
   additional levels of names.

   IPv4 addresses used for tests and in examples are specified in
   [I-D.iana-rfc3330bis], IPv6 addresses used in examples are described
   in [RFC3849]; see also [RFC4085].

   Fully Qualified Domain Names used in many Internet Protocols allow
   only LDH (letter, digit, hyphen) domain labels as described in
   [RFC1123], [RFC3696], and [RFC4343].  The letters are ASCII letters;
   certain LDH-labels are also known as A-labels in the context of IDN
   (Internationalization of Domain Names) and [IDNAbis].

   The key words "MAY", "RECOMMENDED", and "SHOULD" in this memo are to
   be interpreted as described in [RFC2119].

2.  TLDs for Testing, & Documentation Examples

   There is a need for top level domain (TLD) names that can be used for
   creating names which, without fear of conflicts with current or
   future actual TLD names in the global DNS, can be used for private
   testing of existing DNS related code, examples in documentation, DNS
   related experimentation, invalid DNS names, or other similar uses.

   For example, without guidance, a site might set up some local
   additional unused top level domains for testing of its local DNS code
   and configuration.  Later, these TLDs might come into actual use on
   the global Internet.  As a result, local attempts to reference the
   real data in these zones could be thwarted by the local test
   versions.  Or test or example code might be written that accesses a
   TLD that is in use with the thought that the test code would only be
   run in a restricted testbed net or the example never actually run.
   Later, the test code could escape from the testbed or the example be
   actually coded and run on the Internet.  Depending on the nature of
   the test or example, it might be best for it to be referencing a TLD
   permanently reserved for such purposes.

   To safely satisfy these needs, five domain names are reserved as
   listed and described below.  See also Section 4.

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2.1.  ".example", ".tld"

   ".example", ".tld", and the example TLDs in Section 4 are RECOMMENDED
   for use in documentation or as examples.

2.2.  ".invalid"

   ".invalid" is intended for use in online construction of domain names
   that are sure to be invalid, and for which it is obvious at a glance
   that they are invalid.

   Applications MAY treat ".invalid" as what the name says.  For this
   technical reason reserving internationalized ".invalid" TLDs would be

2.3.  ".localhost"

   The ".localhost" TLD has traditionally been statically defined in
   host DNS implementations as having an address record pointing to the
   loop back IP address and is reserved for such use.  Any other use
   would conflict with widely deployed code which assumes this use.

   See [RFC1122] for IPv4 and [RFC4291] for IPv6 loop back addresses.

2.4.  ".test"

   ".test" and the new test TLDs in Section 4 are RECOMMENDED for use in
   testing of current or new DNS related code.  Applications SHOULD
   treat these test TLDs like any other TLD; a special handling could
   defeat the purpose of a test.

3.  Reserved Example Second Level Domain Names

   The Internet Assigned Numbers Authority (IANA) also reserves the
   three second level domain names "", "", and
   "", which can be used in examples as explained in
   Section 2.1.

   When TLDs offer further second level domains for examples, the TLD
   administrators are encouraged to publish the relevant policies in
   their TLD as an informational RFC.

   The second level domain names "nic", "whois", and "www" are often
   reserved or used for administrative purposes of the TLD, e.g.,
   "whois.example" for the fully qualified domain name of a host with a
   whois server.  As with second level domains for examples this can be
   an issue in the case of a TLD redelegation.

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   Please note that there are no globally reserved LDH DNS labels below
   the top level; see [RFC4367].

4.  Internationalization Considerations

   In 2007 IANA created eleven IDN test TLDs together with corresponding
   IDN example labels.  The A-labels, corresponding languages, and IDN
   U-labels are listed below; see [RFC3490] or its [IDNAbis] successor
   for details about IDN.  Applications SHOULD treat the IDN test TLDs
   as explained in Section 2.4.

      TLD A-label          Language      Test U-label (hex. code points)
    ".xn--0zwm56d"         Chinese (simplified)                6d4b 8bd5
    ".xn--11b5bs3a9aj6g"   Hindi             92a 930 940 915 94d 937 93e
    ".xn--80akhbyknj4f"    Russian   438 441 43f 44b 442 430 43d 438 435
    ".xn--9t4b11yi5a"      Korean                         d14c c2a4 d2b8
    ".xn--deba0ad"         Yiddish                       5d8 5e2 5e1 5d8
    ".xn--g6w251d"         Chinese (traditional)               6e2c 8a66
    ".xn--hgbk6aj7f53bba"  Persian           622 632 645 627 6cc 634 6cc
    ".xn--hlcj6aya9esc7a"  Tamil             baa bb0 bbf b9f bcd b9a bc8
    ".xn--jxalpdlp"        Greek                 3b4 3bf 3ba 3b9 3bc 3ae
    ".xn--kgbechtv"        Arabic                625 62e 62a 628 627 631
    ".xn--zckzah"          Japanese                       30c6 30b9 30c8

   The corresponding IDN example labels shown below are reserved as TLDs
   for examples; compare Section 2.1.  Additional IDN example TLDs,
   notably the final list of IDN example labels after the IDN test, can
   be reserved later as specified in Section 5.

      TLD A-label          Language   Example U-label (hex. code points)
    ".xn--9n2bp8q"         Korean                              c2e4 b840
    ".xn--e1afmkfd"        Russian               43f 440 438 43c 435 440
    ".xn--fdbk5d8ap9b8a8d" Yiddish       5d1 5f2 5b7 5e9 5e4 5bc 5d9 5dc
    ".xn--fsqu00a"         Chinese (simplified)                4f8b 5b50
    ".xn--fsqu00a"         Chinese (traditional)               4f8b 5b50
    ".xn--hxajbheg2az3al"  Greek 3c0 3b1 3c1 3ac 3b4 3b5 3b9 3b3 3bc 3b1
    ".xn--mgbh0fb"         Arabic                        645 62b 627 644
    ".xn--mgbh0fb"         Persian                       645 62b 627 644
    ".xn--p1b6ci4b4b3a"    Hindi                 909 926 93e 939 930 923
    ".xn--r8jz45g"         Japanese                            4f8b 3048
    ".xn--zkc6cc5bi7f6e"   Tamil             b89 ba4 bbe bb0 ba3 bae bcd

5.  IANA Considerations

   IANA reserves the TLDs ".example", ".invalid", ".localhost", ".test",
   ".tld", eleven IDN test TLDs, and nine IDN example TLDs as noted

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   above.  IANA reserves the second level domains "",
   "", and "".

   IANA creates a registry of reserved TLDs; this can be done alongside
   existing IANA TLD registries at the discretion of IANA.  The registry
   should contain references to the relevant specifications, for the 25
   reserved TLDs specified here references to this memo will do.

   Additional reserved TLDs require IETF review as defined in [RFC5226]
   section 4.1 in conjunction with clause 4.3 in [RFC2860].

   The *technical* purpose of a reserved TLD has to be stated in its

   Proposals to reserve TLD labels not permitted for ordinary TLDs, as
   specified in [RFC1123] among others, e.g., labels not starting with a
   letter, or not following known LDH- and [IDNAbis] rules, are not
   expected to survive an IETF review without compelling reasons.

6.  Security Considerations

   Confusion and conflict can be caused by the use of a current or
   future top level domain name in experimentation or testing, as an
   example in documentation, to indicate invalid names, or as a synonym
   for the loop back address.  Test and experimental software can escape
   and end up being run against the global operational DNS.  Even
   examples used "only" in documentation can end up being coded and
   released or cause conflicts due to later real use and the possible
   acquisition of intellectual property rights in such "example" names.

   The reservation of several top level domain names for these purposes
   minimizes such confusion and conflict.

   [RFC4367] discusses various false assumptions based on domain labels,
   however this doesn't affect the reserved TLDs in this memo.

   Readers need to be aware that the IANA registry of reserved TLDs in
   Section 5 won't list all reserved TLDs for specific applications and
   protocols.  The registry can only list reserved TLDs if somebody
   bothered to propose it, typically in an Internet-Draft, and the
   proposal was accepted in an IETF review.

7.  Acknowledgments

   This memo contains major parts of [RFC2606] written by Donald E.
   Eastlake and Aliza R. Panitz.

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   Thanks to Alfred Hoenes, Bill McQuillan, Brian Carpenter,
   Dave Cridland, David Conrad, Debbie Garside, Doug Otis, Joe Abley,
   John Klensin, John Levine, Lyman Chapin, Marcel Parodi, Mark Andrews,
   Marshall Eubanks, Michael Dillon, Ole Jacobsen, Paul Hoffman,
   Peter Saint-Andre, Philip Guenther, Philip Hallam-Baker, SM,
   Spencer Dawkins, Steve Crocker, Sumit Pandya, Thomas Narten,
   Tina Dam, Tony Finch, and Tony Hansen for their feedback,
   contributions, or encouragement.

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

8.2.  Informative References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, November 1987.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

   [RFC1122]  Braden, R., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122, October 1989.

   [RFC1123]  Braden, R., "Requirements for Internet Hosts - Application
              and Support", STD 3, RFC 1123, October 1989.

   [RFC1591]  Postel, J., "Domain Name System Structure and Delegation",
              RFC 1591, March 1994.

   [RFC2606]  Eastlake, D. and A. Panitz, "Reserved Top Level DNS
              Names", BCP 32, RFC 2606, June 1999.

   [RFC2860]  Carpenter, B., Baker, F., and M. Roberts, "Memorandum of
              Understanding Concerning the Technical Work of the
              Internet Assigned Numbers Authority", RFC 2860, June 2000.

   [RFC2965]  Kristol, D. and L. Montulli, "HTTP State Management
              Mechanism", RFC 2965, October 2000.

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   [RFC3490]  Faltstrom, P., Hoffman, P., and A. Costello,
              "Internationalizing Domain Names in Applications (IDNA)",
              RFC 3490, March 2003.

   [RFC3696]  Klensin, J., "Application Techniques for Checking and
              Transformation of Names", RFC 3696, February 2004.

   [RFC3849]  Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix
              Reserved for Documentation", RFC 3849, July 2004.

   [RFC3927]  Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
              Configuration of IPv4 Link-Local Addresses", RFC 3927,
              May 2005.

   [RFC4085]  Plonka, D., "Embedding Globally-Routable Internet
              Addresses Considered Harmful", BCP 105, RFC 4085,
              June 2005.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [RFC4343]  Eastlake, D., "Domain Name System (DNS) Case Insensitivity
              Clarification", RFC 4343, January 2006.

   [RFC4367]  Rosenberg, J. and IAB, "What's in a Name: False
              Assumptions about DNS Names", RFC 4367, February 2006.

              Cotton, M., "Special Use IPv4 Addresses",
              draft-iana-rfc3330bis-03 (work in progress), June 2008.

   [IDNAbis]  IETF, "Internationalized Domain Names in Applications
              (Revised)", April 2008,

Appendix A.  Educational Info

   This informative appendix tries to answer three frequently asked

   1.  As of 2008 IANA is the registrant of ""; TLD ".edu"
       has no contract with ICANN; its administration is based on a five
       years contract with the US DoC renewed in 2006; see
       <>.  Under amendment
       6 of their current policy generic names cannot be registered.
       This is not exactly the same situation as for say "",
       where IANA is the registrant *and* registrar.

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   2.  As of 2008 IANA is the registrant of ""; TLD ".info"
       was created by ICANN in 2001.  The ".info" registry agreement
       lists reserved DNS labels including "example"; see
       <> appendix 6 (2006)
       and K (2001), respectively.  This is not exactly the same
       situation as for say "", where IANA is the registrant
       *and* registrar.

   3.  Ignoring [RFC2965] the TLD ".local" issue was discussed in a
       bunch of Internet-Drafts related to AS112, zeroconf, and
       [RFC3927].  Presumably TLD ".local" should be registered as
       reserved for technical reasons, but deserves its own document
       with the fine print.

Appendix B.  Document History

   Changes in version 12:

   o  Version 12 adjusts white space introduced in version 10 that
      should have been removed for version 11.  Version 11 attracted no
      further feedback.

   o  An informal last call on the IDNAbis list for version 10 resulted
      in one change for version 11 as noted below.  Unsurprisingly the
      IDNAbis WG did not adopt this draft as work item.  The WG also did
      not tackle the issue of IDNA <toplabel>s so far, and this memo is
      not the place to update [RFC1123] section 2.1.

   Changes in version 11:

   o  Added nine IDN example labels corresponding to the IDN test labels
      as reserved TLDs after long discussions with two contributors
      confirming the stability and desirability of this approach.

   o  Noted that the list of IDN example TLDs might be extended, and a
      final list can be reserved as specified here after the conclusion
      of the IDN test.

   Changes in version 10:

   o  Noted that only certain LDH-labels are or might be A-labels based
      on feedback.  The details are or will be specified in [IDNAbis].

   o  Moved [RFC2860] back to informative.  Folks *apparently* disagree
      what it should be, more feedback needed to justify a downref.

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   o  Added [RFC3696] again, its description of a <toplabel> covers the
      eleven IDN test TLDs.

   Changes in version 09:

   o  Fixed [RFC2860] link, clause 4.3 is a section of the MoU, not a
      section of the RFC containing this MoU.

   o  Added ".tld" as reserved TLD for examples following a proposal by
      Bill McQuillan supported by some others.

   o  Arguably ".bad" ideas ".bar", ".bat", ".baz", ".foo", and ".lit"
      not yet added for different reasons, they would need stronger

   Changes in version 08:

   o  Moved [RFC2860] to normative, inspired by feedback and the
      precedence in another BCP.  Added the relevant sections in
      [RFC2860] and [RFC5226] to Section 5.

   o  Added a long blurb that the purpose of reserved TLDs has to be
      noted in their specifications, and that reserving TLDs not
      permitted as ordinary TLDs need very good reasons to survive the
      required IETF review.

   o  [IDNAbis] hopefully fixes the <toplabel> problem in [RFC1123].
      This memo isn't the place to do this, as the issue is not limited
      to reserved TLDs, tests, and examples.

   Changes in version 07:

   o  Kept "nic", "whois", and "www" as known examples why there are no
      globally reserved LDH labels for whatever purpose below the top

   o  Proposals to add ".internal", ".local", ".localdomain", and
      ".uucp" not adopted.  This memo covers known test and example
      TLDs, as well as two other TLDs and three example SLDs inherited
      from [RFC2606].  Reserved TLDs for other purposes deserve separate

   o  Added a note that internationalizations of ".invalid" are a non-
      starter, as this TLD is expected to be hardwired in some
      applications.  For ".localhost" that should be obvious.

   o  Review requests sent at different times to the APPS, general,
      [IDNAbis], INT, and OPS mailing lists.

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   Changes in version 06:

   o  Explanations of the terms LDH, A-label, and IDN added in
      Section 1.  Just in case added a reference to [RFC4343].

   o  Downgraded [RFC3696] to [RFC1123]; for some months the best
      documentation of a <toplabel> was available in an erratum.

   Changes in version 05:

   o  Donald offered to co-author this memo.

   o  Clarified that there are now additional TLDs recommended for
      tests, not only the original ".test" in Section 2.4.

   Changes in version 04:

   o  In the "Public Suffix List" debate SM quoted [RFC4085], added to
      Section 1.

   o  Replaced "A record" by "address record" with references to
      [RFC1122] and [RFC4291] in Section 2.3.

   o  Added IDN test U-labels (in a crude hex. format due to RFC layout
      limitations) with the help of <> and

   Changes in version 03:

   o  Swapped IANA and security considerations based on feedback, since
      version 01 the order anyway did not more follow <http://>.

   o  Dave Cridland proposed another [RFC4367] caveat, there are no
      globally reserved LDH labels below the top level.  LDH excludes
      special cases such as the empty label reserved for the root, and
      leaf labels starting with an underscore.

   o  The informative Appendix A hopefully answers frequently asked
      questions about "", "", and ".local".

   Changes in version 02:

   o  Added the related [RFC3849] and [I-D.iana-rfc3330bis] references.
      Added an [RFC4367] reference to the security considerations, as
      this explains one of many issues with any "well-known" label below
      the top level.

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   o  Improved the IANA Considerations Section 5 based on feedback.  The
      registry of reserved TLDs needs references to the relevant

   o  Added a caveat that the IANA registry of reserved TLDs cannot list
      all obscure ideas of specific applications and protocols; somebody
      has to trigger an IETF review for new registrations.

   Changes in version 01:

   o  Various editorial issues found by Tony Hansen fixed.

   o  Added an [IDNAbis] reference.  The authors believe that the IETF
      is not entitled to decree that "" belongs to the set
      of three example-SLDs reserved by IANA.

   Changes in version 00:

   o  John Klensin suggested clarifying the guidelines for examples in
      [RFC2606], referenced by <>.
      Documenting the eleven new IDN test TLDs was anyway desirable.

Authors' Addresses

   Frank Ellermann
   Hamburg, Germany


   Donald E. Eastlake 3rd
   Eastlake Enterprises
   155 Beaver Street
   Milford, MA  01757

   Phone:  +1-508-634-2066

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Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an

Intellectual Property

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   This document was produced using xml2rfc v1.33 (of from a source in RFC-2629 XML format.

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