Network Working Group                                        M. Mealling
Internet-Draft                                                  VeriSign
Expires: April 29, 2002                                      L. Masinter
                                              Adobe Systems Incorporated
                                                               T. Hardie
                                                                G. Klyne
                                                       MIMEsweeper Group
                                                        October 29, 2001

      An IETF URN Sub-namespace for Registered Protocol Parameters

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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Copyright Notice

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


   This document describes a new sub-delegation for the 'ietf' URN
   namespace for registered protocol items.  The 'ietf' URN namespace is
   defined in RFC 2648 as a root for persistent URIs that refer to IETF-
   defined resources.

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1. Introduction

   From time to time IETF standards require the registration of various
   protocol elements in well known central repository.  The Internet
   Assigned Numbers Authority maintains this central repository and
   takes direction from the IETF on what, how and when to add items to
   it.  The IANA maintains lists of items such as all assigned port
   numbers, MIME media types, enterprise numbers, etc.

   Over time there has developed a need to be able to reference these
   elements as URIs in various schema.  In the past this was done in a
   very ad hoc way that easily led to interoperability problems.  This
   document creates a new sub-delegation below the "ietf" [2]URN
   namespace [1] called 'params' which acts as a standardized mechanism
   for naming the items registered for IETF standards.  Any assignments
   below that are specified in an RFC according to the IETF concensus
   process and which include the template found in Section 3.

2. IETF Sub-namespace Specifics

   Sub-namespace name:


   Declared registrant of the namespace:

       The Internet Engineering Task Force

   Declaration of structure:

      The namespace is primarily opaque.  The IANA, as operator of the
      registry, may take suggestions for names to assign but they
      reserve the right to assign whatever name they desire, within
      guidelines set by the IESG.  The colon character (":") is used to
      denote a very limited concept of hierarchy.  If a colon is present
      then the items on both sides of it are valid names.  In general,
      if a name has a colon then the item on the left hand side
      represents a class of those items that would contain other items
      of that class.  For example, a name can be assigned to the entire
      list of DNS resource record type codes as well as for each
      individual code.  The URN for the list might look like this:

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      while the URN for the SOA records type code might look like this:


   Relevant ancillary documentation:

      [3], [2], [1]

   Identifier uniqueness considerations:

      The IESG uses the IETF concensus process to ensure that sub-
      namespaces generate unique names within that sub-namespace.  The
      IESG delegates to the IANA the task of ensuring that the sub-
      namespace names themselves are unique.  Until and unless the IESG
      specifies differently, the IANA is directed to ensure uniqueness
      by comparing the name to be assigned with the list of previously
      assigned names.  In the case of a conflict the IANA is to request
      a new string from the registrant until the conflict is resolved.

   Identifier persistence considerations:

      Once a name has been allocated it MUST NOT be re-allocated for a
      different purpose.  The rules provided for assignments of values
      within a sub-namespace MUST be constructed so that the meaning of
      values cannot change.  This registration mechanism is not
      appropriate for naming values whose meaning may change over time.
      If a value that changes over time the assignment MUST name the
      container or concept that contains the value, not the value
      itself.  For example, if a parameter called 'foo' has a value that
      changes over time, it is valid to create the name
      'urn:ietf:params:foo-params:foo' that identifies that 'slot'.  It
      is not valid to actually create a name that contains that value
      unless it is a persistent and unique value such as a version

   Process of identifier assignment:

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      Identifiers are assigned only after a particular protocol element
      or number has been registered with the IANA using standard
      policies and procedures, or documented in an RFC describing a
      standards track protocol.  This means that the 'gating' function
      for assignment is the "IETF Concensus" process documented in RFC
      2434 [4].

   Process of identifier resolution:

      At this time no resolution mechanism is defined.

   Rules for Lexical Equivalence:

      Lexical equivalence is achieved by exact string match.

   Conformance with URN Syntax:

      There are no additional characters reserved.

   Validation mechanism:




3. Assigning Names

   The creation of a new registry name will be simple for most flat
   registries.  The only required elements will be the registry name , a
   reference to relevant documents, a statement about which
   current/proposed document repositories contains the authoritative
   data for the registry, and a statement specifying which element in
   the registry is the value to be used in the URN.  In most cases this
   last element will be the index value assigned by the IANA.

   More complex registries (DNS Parameters for example) will need to
   repeat that information for any sub-namespaces.  It should also be
   clear as to whether or not a name is assigned to the sub-namespace
   itself (i.e.  is 'urn:ietf:params:dns:rr-types' valid by itself and
   if so, what does it name?).

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   The template:

   Registry name: -- The name of the sub-namespace.  In many cases this
      should be the same name that the IANA calls the registry itself.

   Specification: -- Relevant IETF published documents that define the
      registry and the items in it.

   Repository: -- A pointer to the 'current' location of the registry in
      the protocol parameters repository or the relevant RFCs that
      document the items being named.  This value will change over time
      as the entity that maintains the repository moves files and or
      fileservers.  It is not meant as a permanent binding to the
      filename but as a hint to the IANA for what the initial mapping
      would be.

   Index value: -- Description of how a registered value is to be
      embedded in the URI form.  This MUST include details of any
      transformations that may be needed for the resulting string to
      conform to URN syntax rules and and any canonicalization needed so
      that the case-sensitive string comparison yields the expected

   The process for requesting that a URN be assigned is currently to put
   the above template or a reference to it in the IANA considerations
   section of the specifying document.  Other more automated processes
   may be proposed at a latter time if demand requires it.

4. Security Considerations

   None not already inherent to using URNs.

5. IANA Considerations

   This document puts a new and significant burden on the IANA since it
   may require a additional assignment process to happen for each new
   IANA registry.  To minimize the administrative burden on IANA, any
   parameter namespace registration is very clear about the criteria for
   inclusion in that namespace.

   Defining a registry that fits the constraints of a URN namespace will
   impose extra discipline that should take some of the guess-work about
   creating and maintaining that registry.


   [1]  Moats, R., "URN Syntax", RFC 2141, May 1997.

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   [2]  Moats, R., "A URN Namespace for IETF Documents", RFC 2648,
        August 1999.

   [3]  Daigle, L., van Gulik, D., Iannella, R. and P. Faltstrom, "URN
        Namespace Definition Mechanisms", BCP 33, RFC 2611, June 1999.

   [4]  Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
        Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.

Authors' Addresses

   Michael Mealling
   505 Huntmar Park Drive
   Herndon, VA  22070

   Phone: +1 770 921 2251

   Larry Masinter
   Adobe Systems Incorporated
   345 Park Ave
   San Jose, CA  95110

   Phone: +1 408 536-3024

   Ted Hardie
   901 Marshall Street
   Redwood City, CA  94063


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   Graham Klyne
   MIMEsweeper Group
   1310 Waterside, Arlington Business Park
   Theale, Reading  RG7 4SA

   Phone: +44 118 930 1300
   EMail: GK@ACM.ORG

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