The Internet Assigned Number Authority (IANA) Application Configuration Access Protocol (ACAP) Vendor Subtrees Registry
RFC 6075

Internet Engineering Task Force (IETF)                       D. Cridland
Request for Comments: 6075                                 Isode Limited
Updates: 2244                                              December 2010
Category: Standards Track
ISSN: 2070-1721

The Internet Assigned Number Authority (IANA) Application Configuration
            Access Protocol (ACAP) Vendor Subtrees Registry

Abstract

   The original Application Configuration Access Protocol (ACAP)
   specification included a vendor registry now used in other protocols.
   This document updates the description of this registry, removing the
   need for a direct normative reference to ACAP and removing ambiguity.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6075.

Copyright Notice

   Copyright (c) 2010 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   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.  Conventions Used in This Document . . . . . . . . . . . . . . . 2
   3.  The Vendor Subtree Registry . . . . . . . . . . . . . . . . . . 3
     3.1.  Internationalization  . . . . . . . . . . . . . . . . . . . 3
     3.2.  Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . 4
     3.3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . 4
     3.4.  Changes from RFC 2244 . . . . . . . . . . . . . . . . . . . 5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
     4.1.  Example Registration  . . . . . . . . . . . . . . . . . . . 6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 7

1.  Introduction

   The [ACAP] specification includes the specification and creation of
   the ACAP Vendor Registry, and this registry has subsequently been
   reused by several specifications, including both [ANNOTATE] and
   [METADATA], and is proving to be a useful mechanism for namespacing
   various names to within a specific vendor's scope.

   The use of textual rather than numeric identifiers for vendors
   benefits engineers and operators who are diagnosing protocol problems
   by allowing them some possibility of identifying the origin of a
   vendor attribute without having to look it up in a registry (although
   that remains a necessary fallback).  As such, engineers and operators
   already have to be familiar with international technical English to
   diagnose textual protocol problems, the restriction to ASCII may help
   and is not believed to harm that intended use.  Exposure of vendor
   attributes directly in end-user user interfaces was not an intended
   use of the registry.

   This document merely updates the registry to reduce ambiguity in the
   original specification and dissociates it from the original document
   in all but name, allowing easier referencing.  It replaces Section
   7.4 and portions of Section 4, particularly Section 4.3, of [ACAP].

2.  Conventions Used in This Document

   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 [KEYWORDS].

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   The formal syntax is to be considered normative and is specified
   using [ABNF].  Where a formal syntax and the prose are in conflict,
   the formal syntax takes precedence.

3.  The Vendor Subtree Registry

   A Vendor Token is a UTF-8 string that begins with "vendor." and that
   is followed by the name of the company or product.  This name MUST
   NOT contain any slash character, period, or the percent and asterisk
   characters typically used as wildcards.

   Following this may be names, separated from the Vendor Token by a
   period, which need not be registered, thus forming a complete Vendor
   Name.

3.1.  Internationalization

   Vendor Tokens are able to contain any valid Unicode codepoint,
   encoded as [UTF-8], except the special characters.  Since the
   publication of [ACAP], however, concerns have been raised on the
   handling and comparison of full Unicode strings; therefore, this
   specification restricts the current registrations to the ASCII subset
   of UTF-8.

   Furthermore, characters such as ASCII control characters, most
   whitespace, and quotes are likely to be confusing and have been
   similarly restricted.

   Therefore, this document allows only ASCII letters, digits, the
   hyphen, and space to be used in registrations (the <iana-vendor-tag>
   ABNF production in Section 3.2).

   At the time of publication of this document, no existing
   registrations violate the new restricted syntax on characters allowed
   in registrations.  [ACAP] required all Vendor Tokens to be registered
   with IANA, so the new restriction is not believed to introduce any
   interoperability issue.

   Finally, note that this document does not change the requirement on
   processors to accept other non-ASCII Unicode codepoints in Vendor
   Tokens (the <possible-vendor-tag> ABNF production in Section 3.2).

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3.2.  Formal Syntax

   This syntax draws upon productions found within [ABNF] and [UTF-8].
   Productions replace those in Section 4.3 of [ACAP].

   vendor-name         = vendor-token *("." name-component)

   name-component      = *(name-char / UTF8-2 / UTF8-3 / UTF8-4)

   name-char           = %x01-24 / %x26-29 / %x2B-2D / %x30-7F
                     ;; ASCII-range characters not including ".",
                     ;; "/", "%", or "*".

   vendor-token        = "vendor." vendor-tag
                     ;; MUST be registered with IANA

   vendor-tag          = iana-vendor-tag / possible-vendor-tag

   iana-vendor-tag     = 1*(ALPHA / DIGIT / SP / "-")
                     ;; This production represents
                     ;; allowed forms for registrations
                     ;; under the rules specified in this
                     ;; document.

   possible-vendor-tag = name-component
                     ;; This production represents what
                     ;; applications and specifications
                     ;; MUST be able to accept.

3.3.  Examples

   A company Example, Ltd. might register the Subtree "vendor.example".
   This means it may use "vendor.example", or any name at all beginning
   "vendor.example.", such as "vendor.example.product".

   These names might be used in several protocols, and are reserved in
   all the relevant protocols, so "vendor.example" might be an ACAP
   [ACAP] dataset class name, and "/vendor/vendor.example" might be a
   tree of IMAP ANNOTATE entries [ANNOTATE].

   Example, Ltd. is free to use either "vendor.example", and group
   specific products under it using the relevant protocol's hierarchy --
   perhaps "/shared/vendor/vendor.example/product" annotation
   [ANNOTATE], or using more specific names, such as "/shared/vendor/
   vendor.example.product" annotation.

   Note that the solidus ("/") characters in the examples above are
   protocol delimiters that are themselves not part of the Vendor Token.

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3.4.  Changes from RFC 2244

   This non-normative section details changes from the original
   specification of the registry in RFC 2244.

   o  Vendor Tokens are restricted to ASCII for registration purposes.

   o  Clarifications that "vendor.<company/product name>" means
      "vendor.company name" or "vendor.product name" - "vendor.company/
      product" is and always has been illegal.

   o  Made "vendor.company" a name in its own right - RFC 2244 only
      refers to a prefix of "vendor.company.".

   o  Added example registration, in line with [EXAMPLES].

4.  IANA Considerations

   This specification updates the IANA registry named the ACAP "Vendor
   Subtrees" registry.  IANA has updated the registry to point at this
   document.

   Vendors may reserve a portion of the ACAP namespace, which is also
   used as the namespace for several other protocols, for private use.
   Vendor Names are reserved for use by that company or product,
   wherever used, once registered.  Registration is on a first come,
   first served basis.  Whenever possible, private attributes and
   classes should be eschewed in favour of improving interoperable
   protocols.

   Vendors may only use names conforming to iana-vendor-tag at the
   current time; future revisions of this specification may change this.

   To: iana@iana.org
   Subject: Registration of ACAP Vendor Subtree

   Private Prefix: vendor.name

   Person and email address to contact for further information:

   (company names and addresses should be included where appropriate)

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4.1.  Example Registration

   IANA is requested to add the following registration, for use by
   specification authors in examples, similarly to the domains specified
   in [EXAMPLES]:

   To: iana@iana.org
   Subject: Registration of ACAP Vendor Subtree

   Private Prefix: vendor.example

   Person and email address to contact for further information:

   Dave Cridland <dave.cridland@isode.com>

5.  Security Considerations

   There are no known security issues with this registry.  Individual
   protocols using Vendor Subtree names may have security issues, and
   the introduction of Unicode has, in itself, security implications --
   the restriction of this is thought to mitigate these.

6.  Acknowledgements

   Thanks must go to Chris Newman, John Myers, and the other designers
   of ACAP for the initial creation of the registry.  Thanks also to
   Alexey Melnikov for advice on this revision.

7.  References

7.1.  Normative References

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

   [ACAP]     Newman, C. and J. Myers, "ACAP -- Application
              Configuration Access Protocol", RFC 2244, November 1997.

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

   [UTF-8]    Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

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7.2.  Informative References

   [ANNOTATE]
              Daboo, C. and R. Gellens, "Internet Message Access
              Protocol - ANNOTATE Extension", RFC 5257, June 2008.

   [EXAMPLES]
              Eastlake 3rd, D. and A. Panitz, "Reserved Top Level DNS
              Names", BCP 32, RFC 2606, June 1999.

   [METADATA]
              Daboo, C., "The IMAP METADATA Extension", RFC 5464,
              February 2009.

Author's Address

   Dave Cridland
   Isode Limited
   5 Castle Business Village
   36, Station Road
   Hampton, Middlesex  TW12 2BX
   GB

   EMail: dave.cridland@isode.com

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