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Individual submission                                         L-J. Liman
Internet-Draft                                                Autonomica
Updates: RFC 1123                                          March 4, 2009
(if approved)
Intended status: Standards Track
Expires: September 5, 2009


                  Top Level Domain Name Specification
                        draft-liman-tld-names-00

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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   This Internet-Draft will expire on September 5, 2009.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
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Abstract

   RFC 1123 is ambiguous regarding the specification for top level
   domain (TLD) labels used in the domain name system.  This document
   clarifies the specification, and aligns it with current praxis,
   including the use of Internationalized Domain Name (IDN) Labels in
   TLD names.


Table of Contents

   1.  Introduction and Background . . . . . . . . . . . . . . . . . . 3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . . . 3
   2.  Technical specification for Top Level Domain Labels . . . . . . 4
   3.  Other Limitations on Top Level Domain Labels  . . . . . . . . . 5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 9





























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1.  Introduction and Background

   RFC 1123 [RFC1123] is ambiguous regarding the specification for top
   level domain (TLD) labels used in the domain name system.  There are
   different interpretations which leads to problems when deciding on
   new TLD names.  One important aspect of this is the wish to use
   internationalized domain name (IDN, RFC 3490 et. al.  [RFC3490])
   labels in top level domains to facilitate use of local scripts.

   This document strives to make a new and clear definition of which
   character sequences are allowed in TLD labels.

   This document is a proposal and a work in progress.

1.1.  Terminology

   The terminology used in this document is as defined in RFC 0952
   [RFC0952] and RFC 1035 [RFC1035].

1.2.  Requirements Language

   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 RFC 2119 [RFC2119].



























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2.  Technical specification for Top Level Domain Labels

   RFC 952 [RFC0952] gives the specification for names that may be used
   for host names on the Internet.  It is updated by RFC 1123 [RFC1123],
   which relaxes the specification somewhat.  It is somewhat unclear
   wheter the relaxation is per label or per entire host name.

   In order to avoid problems based on lack of clarity, the
   specification for a TLD name is hereby stated to be as follows:

   A TLD label MUST be at least two characters long and MAY be as long
   as 63 characters - not counting any leading or trailing periods (.).
   It MUST consist of only ASCII characters from the groups "letters"
   (A-Z), "digits" (0-9) and "hyphen" (-), and it MUST start with an
   ASCII "letter", and it MUST NOT end with a "hyphen".  Upper and lower
   case MAY be mixed at random, since DNS lookups are case-insensitive.

   Hence, the ABNF expression that matches a valid TLD label is as
   follows:


           tldlabel = ALPHA *61(ldh) ld
           ldh      = ld / "-"
           ld       = ALPHA / DIGIT
           ALPHA    = %x41-5A / %x61-7A   ; A-Z / a-z
           DIGIT    = %x30-39             ; 0-9


   This new specification reflects current praxis in registration of TLD
   names by the IANA, and allows for IDNs.





















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3.  Other Limitations on Top Level Domain Labels

   It is carefully noted that the above specification is not the only
   limiting factor on TLD labels.  There may be other entities than the
   IETF that have influence over TLD names, and which may decide to
   restrict the names further.  The above technical specification is
   just one limiting factor.












































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4.  IANA Considerations

   This memo changes the specifications for TLD names registered by the
   IANA, and the IANA is requested to change its registration process to
   use the above specification.














































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5.  Security Considerations

   This document does not introduce any new security issues.

   It may introduce stability issues where names registered under this
   new specification may interoperate badly with old software written to
   enforce a strict interpretation of the old specification.  However,
   it is belived that such software is scarce on the Internet, and since
   TLD names that do not adhere to a strict interpretation of the old
   specification are already used (including IDNs) without apparent
   problems, it is believed that this change of the specicification will
   not create major stability problems on the Internet.







































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6.  References

6.1.  Normative References

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

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

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

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

6.2.  Informative References

   [RFC0952]  Harrenstien, K., Stahl, M., and E. Feinler, "DoD Internet
              host table specification", RFC 952, October 1985.






























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Author's Address

   Lars-Johan Liman
   Autonomica AB
   Bellmansgatan 30
   SE-118 47 Stockholm
   Sweden

   Email: liman@autonomica.se
   URI:   http://www.autonomica.se/









































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