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rfc:rfc2606

Network Working Group D. Eastlake Request for Comments: 2606 A. Panitz BCP: 32 June 1999 Category: Best Current Practice

                    Reserved Top Level DNS Names

Status of this Memo

 This document specifies an Internet Best Current Practices for the
 Internet Community, and requests discussion and suggestions for
 improvements.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1999).  All Rights Reserved.

Abstract

 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.

Table of Contents

 1. Introduction............................................1
 2. TLDs for Testing, & Documentation Examples..............2
 3. Reserved Example Second Level Domain Names..............2
 4. IANA Considerations.....................................3
 5. Security Considerations.................................3
 References.................................................3
 Authors' Addresses.........................................4
 Full Copyright Statement...................................5

1. Introduction

 The global Internet Domain Name System is documented in [RFC 1034,
 1035, 1591] and numerous additional Requests for Comment.  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.

Eastlake & Panitz Best Current Practice [Page 1] RFC 2606 Reserved Top Level DNS Names June 1999

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, four domain names are reserved as
 listed and described below.
                 .test
              .example
              .invalid
            .localhost
    ".test" is recommended for use in testing of current or new DNS
    related code.
    ".example" is recommended for use in documentation or as examples.
    ".invalid" is intended for use in online construction of domain
    names that are sure to be invalid and which it is obvious at a
    glance are invalid.
    The ".localhost" TLD has traditionally been statically defined in
    host DNS implementations as having an A 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.

3. Reserved Example Second Level Domain Names

 The Internet Assigned Numbers Authority (IANA) also currently has the
 following second level domain names reserved which can be used as
 examples.

Eastlake & Panitz Best Current Practice [Page 2] RFC 2606 Reserved Top Level DNS Names June 1999

      example.com
      example.net
      example.org

4. IANA Considerations

 IANA has agreed to the four top level domain name reservations
 specified in this document and will reserve them for the uses
 indicated.

5. 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
 will minimize such confusion and conflict.

References

 [RFC 1034] Mockapetris, P., "Domain names - concepts and facilities",
            STD 13, RFC 1034, November 1987.
 [RFC 1035] Mockapetris, P., "Domain names - implementation and
            specification", STD 13, RFC 1035, November 1987.
 [RFC 1591] Postel, J., "Domain Name System Structure and Delegation",
            RFC 1591, March 1994.

Eastlake & Panitz Best Current Practice [Page 3] RFC 2606 Reserved Top Level DNS Names June 1999

Authors' Addresses

 Donald E. Eastlake 3rd
 IBM
 65 Shindegan Hill Road, RR #1
 Carmel, NY 10512
 Phone: +1 914-276-1668(h)
        +1 914-784-7913(w)
 FAX:   +1 914-784-3833(3)
 EMail: dee3@us.ibm.com
 Aliza R. Panitz
 500 Stamford Dr. No. 310
 Newark, DE 19711 USA
 Phone: +1 302-738-1554
 EMail: buglady@fuschia.net

Eastlake & Panitz Best Current Practice [Page 4] RFC 2606 Reserved Top Level DNS Names June 1999

Full Copyright Statement

 Copyright (C) The Internet Society (1999).  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.

Eastlake & Panitz Best Current Practice [Page 5]

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