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Versions: (draft-saintandre-urnbis-3406bis) 00 01 02 03 04 05 06 07 08 09 draft-ietf-urnbis-rfc2141bis-urn

URNBIS                                                    P. Saint-Andre
Internet-Draft                                                      &yet
Obsoletes: 3406 (if approved)                          February 12, 2014
Intended status: Best Current Practice
Expires: August 16, 2014


      Uniform Resource Name (URN) Namespace Definition Mechanisms
               draft-ietf-urnbis-rfc3406bis-urn-ns-reg-09

Abstract

   This document supplements the Uniform Resource Name (URN) syntax
   specification by defining the concept of a URN namespace, as well as
   mechanisms for defining and registering such namespaces.  This
   document obsoletes RFC 3406.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 16, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  What is a URN Namespace?  . . . . . . . . . . . . . . . . . .   3
   4.  URN Namespace Types . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Formal Namespaces . . . . . . . . . . . . . . . . . . . .   5
     4.2.  Informal Namespaces . . . . . . . . . . . . . . . . . . .   6
   5.  Defining a URN Namespace  . . . . . . . . . . . . . . . . . .   7
     5.1.  Purpose . . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.2.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     5.3.  Assignment  . . . . . . . . . . . . . . . . . . . . . . .   8
     5.4.  Security and Privacy  . . . . . . . . . . . . . . . . . .   9
     5.5.  Resolution  . . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Registration Template . . . . . . . . . . . . . . . . . . . .  10
     6.1.  Namespace ID  . . . . . . . . . . . . . . . . . . . . . .  10
     6.2.  Version . . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.3.  Date  . . . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.4.  Registrant  . . . . . . . . . . . . . . . . . . . . . . .  10
     6.5.  Purpose . . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.6.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.7.  Assignment  . . . . . . . . . . . . . . . . . . . . . . .  10
     6.8.  Resolution  . . . . . . . . . . . . . . . . . . . . . . .  10
     6.9.  Documentation . . . . . . . . . . . . . . . . . . . . . .  11
   7.  Registering a URN Namespace . . . . . . . . . . . . . . . . .  11
     7.1.  Formal Namespaces . . . . . . . . . . . . . . . . . . . .  11
     7.2.  Informal Namespaces . . . . . . . . . . . . . . . . . . .  11
   8.  Guidelines for Designated Experts . . . . . . . . . . . . . .  12
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   10. Security and Privacy Considerations . . . . . . . . . . . . .  12
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     11.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Appendix A.  Changes from RFC 3406  . . . . . . . . . . . . . . .  14
   Appendix B.  Contributors . . . . . . . . . . . . . . . . . . . .  14
   Appendix C.  Acknowledgements . . . . . . . . . . . . . . . . . .  14
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   A Uniform Resource Name (URN) [I-D.ietf-urnbis-rfc2141bis-urn] is a
   Uniform Resource Identifier (URI) [RFC3986] that is intended to serve
   as a persistent, location-independent resource identifier.  This
   document supplements the Uniform Resource Name (URN) syntax
   specification [I-D.ietf-urnbis-rfc2141bis-urn] by defining:

   1.  The concept of a URN namespace.




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   2.  A mechanism for defining a URN namespace and associating it with
       a public identifier (called a Namespace ID or "NID").

   3.  Procedures for registering NIDs with the Internet Assigned
       Numbers Authority (IANA).

   Syntactically, the NID follows the 'urn' scheme name.  For instance,
   a URN in the 'example' namespace [RFC6963] might be of the form
   "urn:example:foo".

   This document rests on two key assumptions:

   1.  Assignment of a URN is a managed process.

       A string that conforms to the URN syntax is not necessarily a
       valid URN, because a URN needs to be assigned according to the
       rules of a particular namespace (in terms of syntax, semantics,
       and process).

   2.  The space of URN namespaces is itself managed.

       A string in the namespace identifier slot of the URN syntax is
       not necessarily a valid URN namespace identifier, because in
       order to be valid a namespace needs to be defined and registered
       in accordance with the rules of this document.

   URN namespaces were originally defined in [RFC2611], which was
   obsoleted by [RFC3406].  Based on experience with defining and
   registering URN namespaces since that time, this document specifies
   URN namespaces with the smallest reasonable set of changes from
   [RFC3406], while at the same time simplifying the registration
   process.  This document obsoletes RFC 3406.

2.  Terminology

   Several important terms used in this document are defined in the URN
   syntax specification [I-D.ietf-urnbis-rfc2141bis-urn].

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

3.  What is a URN Namespace?

   A URN namespace is a collection of identifiers that are (1) unique,
   (2) assigned in a consistent way, and (3) assigned according to a
   common definition.



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   1.  The "uniqueness" constraint means that an identifier within the
       namespace is never assigned to more than one resource and never
       reassigned to a different resource, even if the identifier itself
       is deprecated or becomes obsolete.

   2.  The "consistent assignment" constraint means that an identifier
       within the namespace is assigned by an organization or created in
       accordance with a process or algorithm that is always followed.

   3.  The "common definition" constraint means that there are clear
       definitions for the syntax of identifiers within the namespace
       and the process of assigning or creating them.

   A URN namespace is identified by a particular NID in order to ensure
   the global uniqueness of URNs and, optionally, to provide a cue
   regarding the structure of URNs assigned within a namespace.

   With regard to global uniqueness, using different NIDs for different
   collections of identifiers ensures that no two URNs will be the same
   for different resources, since each collection is required to
   uniquely assign each identifier.  However, a single resource can have
   more than one URN assigned to it for different purposes (e.g., some
   numbers might be valid identifiers in two different identifier
   systems, where the namespace identifier differentiates between the
   resulting URNs).

   With regard to the structure of URNs assigned within a namespace, the
   development of an identifier structure (and thereby a collection of
   identifiers) depends on the requirements of the community defining
   the identifiers, how the identifiers will be assigned and used, etc.
   These issues are beyond the scope of URN syntax and the general rules
   for URN namespaces, because they are specific to the community
   defining a namespace (e.g., the bibliographic and publishing
   communities in the case of the 'ISBN' and 'ISSN' namespaces, or the
   developers of extensions to the Extensible Messaging and Presence
   Protocol in the case of the 'XMPP' namespace).

   URN namespaces inherit certain rights and responsibilities by the
   nature of URNs [I-D.ietf-urnbis-rfc2141bis-urn], e.g.:

   1.  They uphold the general principles of a well-managed URN
       namespace by providing persistent identification of resources and
       unique assignment of identifier strings.

   2.  They can be registered in global registration services.






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4.  URN Namespace Types

   There are two types of URN namespace: formal and informal.  These are
   distinguished by the expected level of service, the information
   needed to define the namespace, and the procedures for registration.
   Because the majority of the namespaces registered so far have been
   formal, this document concentrates on formal namespaces.

   Note: [RFC3406] defined a third type of "experimental namespaces",
   denoted by prefixing the namespace identifier with the string "X-".
   Consistent with [RFC6648], this specification removes the
   experimental category.  Because experimental namespaces were never
   registered, removing the experimental category has no impact on the
   existing registries or future registration procedures.

4.1.  Formal Namespaces

   A formal namespace provides benefit to some subset of users on the
   Internet (e.g., it would not make sense for a formal namespace to be
   used only by a community or network that is not connected to the
   Internet).  For example, it would be inappropriate for a NID to
   effectively force someone to use a proprietary network or service not
   open to the general Internet user.  The intent is that, while the
   community of those who might actively use the names assigned within
   that NID might be small, the potential use of identifiers within that
   NID is open to any user on the Internet.  Formal NIDs might be
   appropriate when some aspects are not fully open.  For example, a
   namespace might make use of a fee-based, privately managed, or
   proprietary registry for assignment of URNs in the namespace.
   However, it might still benefit some Internet users if the associated
   services have openly-published access protocols.

   An organization that will assign URNs within a formal namespace ought
   to meet the following criteria:

   1.  Organizational stability and the ability to maintain the URN
       namespace for a long time; absent such evidence, it ought to be
       clear how the namespace can remain viable if the organization can
       no longer maintain the namespace.

   2.  Competency in name assignment.  This will improve the likelihood
       of persistence (e.g. to minimize the likelihood of conflicts).

   3.  Commitment to not reassigning existing names and to allowing old
       names to continue to be valid, even if the owners or assignees of
       those names are no longer members or customers of that
       organization.  With regard to URN resolution [RFC2276], this does




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       not mean that there needs to be resolution of such names, only
       that the names will not resolve to false or stale information.

   A formal namespace establishes a particular NID, subject to the
   following constraints (above and beyond the syntax rules specified in
   [I-D.ietf-urnbis-rfc2141bis-urn]):

   1.  It MUST NOT be an already-registered NID.

   2.  It MUST NOT start with "urn-" (which is reserved for informal
       namespaces).

   3.  It MUST be more than two characters long.

   4.  It MUST NOT start with "aa-", where "aa" is any combination of
       two ASCII letters.

   5.  It MUST NOT start with the string "xn--", which is reserved for
       potential representation of DNS A-labels in the future [RFC5890].

   All two-letter combinations, and all two-letter combinations followed
   by "-" and any sequence of valid NID characters, are reserved for
   potential use as countrycode-based NIDs for eventual national
   registrations of URN namespaces.  The definition and scoping of rules
   for allocation of responsibility for such countrycode-based
   namespaces is beyond the scope of this document.

4.2.  Informal Namespaces

   Informal namespaces are full-fledged URN namespaces, with all the
   associated rights and responsibilities.  Informal namespaces differ
   from formal namespaces in the process for assigning a NID: for an
   informal namespace, the registrant does not designate the NID;
   instead, IANA assigns a NID consisting of the string 'urn-' followed
   by one or more digits (e.g., "urn-7") where the digits consist of the
   next available number in the sequence of positive integers assigned
   to informal namespaces.  Thus the syntax of an informal namespace is:

       "urn-" <number>

   The only restrictions on <number> are that it (1) consist strictly of
   ASCII digits and (2) not cause the NID to exceed the length
   limitations defined in the URN syntax specification
   [I-D.ietf-urnbis-rfc2141bis-urn].







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5.  Defining a URN Namespace

   The definition of a formal namespace ought to pay particular
   attention to:

   1.  The purpose of the namespace.

   2.  The syntax of URNs assigned within the namespace.

   3.  The process for assigning URNs within the namespace.

   4.  The security implications of assigning and using the assigned
       URNs.

   5.  Optionally, the process for resolving URNs issued within the
       namepace.

   The following sections explain these matters in greater detail.  For
   convenience, a template for defining and registering a URN namespace
   is provided under Section 6.  This information can be especially
   helpful to entities that wish to request assignment of a URN in a
   namespace and to entities that wish to provide URN resolution for a
   namespace.

5.1.  Purpose

   The "Purpose" section of the template describes matters such as:

   1.  The kinds of resources identified by URNs assigned within the
       namespace.

   2.  Why it is preferable to use URNs rather than some other
       technology (e.g., URIs) and why no existing URN namespace is a
       good fit.

   3.  The kinds of software applications that can use or resolve the
       assigned URNs (e.g., by differentiating among disparate
       namespaces, identifying resources in a persistent fashion, or
       meaningfully resolving and accessing services associated with the
       namespace).

   4.  The scope of the namespace (public vs. private, global vs. local
       to a particular organization, nation, or industry).  For example,
       a namespace claiming to deal in "national identification numbers"
       ought to have a global scope and address all identity number
       structures, whereas a URN scheme for a particular national
       identification number system would need to handle only the
       structure for that nation's identity numbers.



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   5.  How the intended community (and the Internet community at large)
       will benefit from using or resolving the assigned URNs.

5.2.  Syntax

   The "Syntax" section of the template describes:

   1.  A description of the structure of URNs within the namespace, in
       conformance with the fundamental URN syntax
       [I-D.ietf-urnbis-rfc2141bis-urn].  The structure might be
       described in terms of a formal definition (e.g., using Augmented
       BNF for Syntax Specifications (ABNF) as specified in [RFC5234]),
       an algorithm for generating conformant URNs, a regular expression
       for parsing the identifier into components, or by explaining that
       the structure is opaque.

   2.  Any special character encoding rules for assigned URNs (e.g.,
       which character ought to always be used for single-quotes).

   3.  Rules for determining equivalence between two identifiers in the
       namespace.  Such rules ought to always have the effect of
       eliminating false negatives that might otherwise result from
       comparison.  If it is appropriate and helpful, reference can be
       made to the equivalence rules defined in the URI specification
       [RFC3986].  Examples of equivalence rules include equivalence
       between uppercase and lowercase characters in the Namespace
       Specific String, between hyphenated and non-hyphenated groupings
       in the identifier string, or between single-quotes and double-
       quotes.  (Note that these are not normative statements for any
       kind of best practice related to handling of equivalences between
       characters in general; they are statements limited to one
       particular namespace only.)

   4.  Any special considerations necessary for conforming with the URN
       syntax.  This is particularly applicable in the case of legacy
       naming systems that are used in the context of URNs.  For
       example, if a namespace is used in contexts other than URNs, it
       might make use of characters that are reserved in the URN syntax.
       This section ought to note any such characters, and outline
       necessary mappings to conform to URN syntax.  Normally, this will
       be handled by percent-encoding the character as specified in the
       URI specification [RFC3986].

5.3.  Assignment

   The "Assignment" section of the template describes matters such as:





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   1.  Mechanisms or authorities for assigning URNs to resources.  It
       ought to make clear whether assignment is completely open (e.g.,
       following a particular algorithm), completely closed (e.g., for a
       private organization), or limited in various ways (e.g.,
       delegated to authorities recognized by a particular
       organization); if limited, it ought to explain how to become an
       assigner of identifiers or how to request assignemtn of
       identifers from existing assignment authorities.

   2.  Methods for ensuring that URNs within the namespace are unique.
       For example, identifiers might be assigned sequentially or in
       accordance with some well-defined process by a single authority,
       assignment might be partitioned among delegated authorities that
       are individually responsible for respecting uniqueness rules, or
       URNs might be created independently following an algorithm that
       itself guarantees uniqueness.

5.4.  Security and Privacy

   The "Security" section of the template describes any potential issues
   related to security and privacy with regard to assignment, use, and
   resolution of identifiers within the namespace.  Examples of such
   issues include the consequences of producing false negatives and
   false positives during comparison for equivalence (see also
   [RFC6943]), leakage of private information when identifiers are
   communicated on the public Internet, the potential for directory
   harvesting, and various issues discussed in the guidelines for
   security considerations in RFCs [RFC3552] and the privacy
   considerations for Internet protocols [RFC6973].

5.5.  Resolution

   The "Resolution" section specifies the rules for resolution of URNs
   assigned within the namespace.  If such URNs are intended to be
   resolvable, the namespace needs to be registered in a Resolution
   Discovery System (RDS, see [RFC2276]) such as DDDS.  Resolution then
   proceeds according to standard URI resolution processes, as well as
   the mechanisms of the RDS.  This section ought to lists the
   requirements for becoming a recognized resolver of URNs in the
   relevant namespace (and being so listed in the RDS registry).
   Answers might include, but are not limited to:

   1.  The namespace is not listed with an RDS; therefore this section
       is not applicable.

   2.  Resolution mirroring is completely open, with a mechanism for
       updating an appropriate RDS.




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   3.  Resolution is controlled by entities to which assignment has been
       delegated.

6.  Registration Template

6.1.  Namespace ID

   Requested of IANA (formal) or assigned by IANA (informal).

6.2.  Version

   The version of the registration, starting with 1 and incrementing by
   1 with each new version.

6.3.  Date

   The date when the registration is requested of IANA, using the format
   YYYY-MM-DD.

6.4.  Registrant

   The person or organization that has registered the NID, including the
   following information:

   o  The name and address of the registering organization.

   o  The name and contact information (email, phone number, and/or
      postal address) of the designated contact person.

6.5.  Purpose

   Described under Section 5.1 of this document.

6.6.  Syntax

   Described under Section 5.2 of this document.

6.7.  Assignment

   Described under Section 5.3 of this document.

6.8.  Resolution

   Described under Section 5.5 of this document.







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6.9.  Documentation

   A pointer to an RFC, a specification published by another standards
   development organization, or another stable document that provides
   further information about the namespace.

7.  Registering a URN Namespace

7.1.  Formal Namespaces

   The registration policy for formal namespaces is Expert Review as
   defined in the "IANA Considerations" document [RFC5226].  The key
   steps for registration of a formal namespace are:

   1.  Fill out the namespace registration template (see Section 6).
       This can be done as part of an Internet-Draft or a specification
       in another series, although that is not necessary.

   2.  Send the completed template to the urn-nid@ietf.org discussion
       list for review.

   3.  If necessary to address comments received, repeat steps 1 and 2.

   4.  If the designated experts approve the request, the IANA will
       register the requested NID.

   A formal namespace registration can be revised by updating the
   registration template, following the same steps outlined above for
   new registrations.  A revised registration should making special note
   of any relevant changes in the underlying technologies or namespace
   management processes.

7.2.  Informal Namespaces

   The registration policy for informal namespaces is First Come First
   Served [RFC5226].  The key steps for registration of an informal
   namespace are:

   1.  Write a completed namespace definition template (see Section 6).

   2.  Send it to the urn-nid@ietf.org discussion list for feedback.

   3.  Once the review period has expired, send the final template to
       IANA (via the iana@iana.org email address).

   An informal namespace registration can be revised by updating the
   registration template, following the same steps outlined above for
   new registrations.



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8.  Guidelines for Designated Experts

   Experience to date with NID registration requests has shown that
   registrants sometimes do not initially understand some of the
   subtleties of URN namespaces, and that defining the namespace in the
   form of a specification enables the registrants to clearly formulate
   their "contract" with the intended user community.  Therefore,
   although the registration policy for formal namespaces is Expert
   Review and a stable specification is not strictly required, the
   designated experts for NID registration requests ought to encourage
   applicants to provide a stable specification documenting the
   namespace definition.

   Naming can be difficult and contentious; the designated experts and
   applicants are strongly encouraged to work together in a spirit of
   good faith and mutual understanding to achieve rough consensus on
   progressing registrations through the process.  They are also
   encouraged to bring additional expertise into the discussion if that
   would be helpful in adding perspective or otherwise resolving issues.

9.  IANA Considerations

   This document outlines the processes for registering URN namespaces,
   and has implications for the IANA in terms of registries to be
   maintained.  In all cases, the IANA ought to assign the appropriate
   NID (formal or informal) once the procedures outlined in this
   document have been completed.

10.  Security and Privacy Considerations

   This document largely focuses on providing mechanisms for the
   declaration of public information.  Nominally, these declarations
   will be of relatively low security profile, however there is always
   the danger of "spoofing" and providing misinformation.  Information
   in these declarations ought to be taken as advisory.

   The definition of a URN namespace needs to account for potential
   security and privacy issues related to assignment, use, and
   resolution of identifiers within the namespace.

11.  References

11.1.  Normative References

   [I-D.ietf-urnbis-rfc2141bis-urn]
              Saint-Andre, P., Ed., "Uniform Resource Name (URN)
              Syntax", draft-ietf-urnbis-rfc2141bis-urn-07 (work in
              progress), January 2014.



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

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66, RFC
              3986, January 2005.

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

11.2.  Informative References

   [RFC2276]  Sollins, K., "Architectural Principles of Uniform Resource
              Name Resolution", RFC 2276, January 1998.

   [RFC2611]  Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
              "URN Namespace Definition Mechanisms", BCP 33, RFC 2611,
              June 1999.

   [RFC3406]  Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
              "Uniform Resource Names (URN) Namespace Definition
              Mechanisms", BCP 66, RFC 3406, October 2002.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552, July
              2003.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

   [RFC5890]  Klensin, J., "Internationalized Domain Names for
              Applications (IDNA): Definitions and Document Framework",
              RFC 5890, August 2010.

   [RFC6648]  Saint-Andre, P., Crocker, D., and M. Nottingham,
              "Deprecating the "X-" Prefix and Similar Constructs in
              Application Protocols", BCP 178, RFC 6648, June 2012.

   [RFC6943]  Thaler, D., "Issues in Identifier Comparison for Security
              Purposes", RFC 6943, May 2013.

   [RFC6963]  Saint-Andre, P., "A Uniform Resource Name (URN) Namespace
              for Examples", BCP 183, RFC 6963, May 2013.







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   [RFC6973]  Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
              Morris, J., Hansen, M., and R. Smith, "Privacy
              Considerations for Internet Protocols", RFC 6973, July
              2013.

Appendix A.  Changes from RFC 3406

   This document makes the following substantive changes from [RFC3406]:

   1.  Relaxes the registration policy for formal namespaces from "IETF
       Review" to "Expert Review" [RFC5226].

   2.  Removes the category of experimental namespaces, consistent with
       [RFC6648].

   3.  Simplifies the registration template.

   In addition, some of the text has been updated to be consistent with
   the definition of Uniform Resource Identifiers (URIs) [RFC3986] and
   the processes for registering information with the IANA [RFC5226], as
   well as more modern guidance with regard to security issues [RFC3552]
   and identifier comparison [RFC6943].

Appendix B.  Contributors

   RFC 3406, which provided the basis for this document, was authored by
   Leslie Daigle, Dirk-Willem van Gulik, Renato Iannella, and Patrik
   Faltstrom.  Their work is gratefully acknowledged.

Appendix C.  Acknowledgements

   Thanks to Marc Blanchet, Juha Hakala, Paul Jones, John Klensin, and
   Barry Leiba for their input.

Author's Address

   Peter Saint-Andre
   &yet

   Email: ietf@stpeter.im











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