RFC3553: An IETF URN Sub-namespace for Registered Protocol Parameters

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Related keywords:  (syntax) (uniform resource names)

Network Working Group                                        M. Mealling
Request for Comments: 3553                                      VeriSign
BCP: 73                                                      L. Masinter
Category: Best Current Practice                            Adobe Systems
                                                               T. Hardie
                                                                G. Klyne
                                                            Nine by Nine
                                                               June 2003

      An IETF URN Sub-namespace for Registered Protocol Parameters

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 (2003).  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.

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 consensus
   process and which include the template found in Section 4.

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2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119.

3.  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:


      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 consensus 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

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      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:

      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 Consensus" 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 according to
      the rules for URN syntax found in RFC 2141 [1].  Specifically, due
      to the URN syntax definitions, the 'stringprep' standard found in
      RFC 3454 [7] does not apply.

   Conformance with URN Syntax:

      There are no additional characters reserved.

   Validation mechanism:


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4.  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?).

   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 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.

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5.  Security Considerations

   None not already inherent to using URNs.  Security considerations for
   URNs in general can be found in RFC 2141 [1].  Further security
   considerations for one specific URN resolution method can be found in
   Dynamic Delegation  Discovery System (DDDS) Part Four: The Uniform
   Resource Identifiers (URI) Resolution Application (RFC 3404) [5]
   which is part of a series starting with Dynamic  Delegation Discovery
   System (DDDS) Part One: The Comprehensive DDDS  (RFC 3401) [6].

6.  IANA Considerations

   This document puts a new and significant burden on the IANA since it
   may require an 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.

7.  Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive

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8.  Normative References

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

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

   [3]  Daigle, L., van Gulik, D., Iannella, R. and P. Faltstrom,
        "Uniform Resource Names (URN) Namespace Definition Mechanisms",
        BCP 66, RFC 3406, October 2002.

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

   [5]  Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
        Four: The Uniform Resource Identifiers (URI)", RFC 3404,
        February 2002.

   [6]  Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
        One: The Comprehensive DDDS", RFC 3401, May 2002.

   [7]  Hoffman, P. and M. Blanchet, "Preparation of Internationalized
        Strings ("stringprep")", RFC 3454, December 2002.

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9.  Authors' Addresses

   Michael Mealling
   21345 Ridgetop Circle
   Sterling, VA  20166

   EMail: michael@verisignlabs.com, michael@neonym.net
   URI:   http://www.verisign.com

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

   Phone: +1 408 536-3024
   EMail: LMM@acm.org
   URI:   http://larry.masinter.net

   Ted Hardie
   Qualcomm, Inc.
   675 Campbell Technology Parkway
   Suite 200
   Campbell, CA

   EMail: hardie@qualcomm.com

   Graham Klyne
   Nine by Nine

   EMail: GK-IETF@ninebynine.org
   URI:   http://www.ninebynine.net/

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10.  Full Copyright Statement

   Copyright (C) The Internet Society (2003).  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

   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


   Funding for the RFC Editor function is currently provided by the
   Internet Society.

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