    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.

    Cridland                     Standards Track                    [Page 1]

    RFC 6075              ACAP Vendor Subtrees Registry        December 2010

    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].

    Cridland                     Standards Track                    [Page 2]

    RFC 6075              ACAP Vendor Subtrees Registry        December 2010

       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).

    Cridland                     Standards Track                    [Page 3]

    RFC 6075              ACAP Vendor Subtrees Registry        December 2010

    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.

    Cridland                     Standards Track                    [Page 4]

    RFC 6075              ACAP Vendor Subtrees Registry        December 2010

    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)

    Cridland                     Standards Track                    [Page 5]

    RFC 6075              ACAP Vendor Subtrees Registry        December 2010

    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.

    Cridland                     Standards Track                    [Page 6]

    RFC 6075              ACAP Vendor Subtrees Registry        December 2010

    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

    Cridland                     Standards Track                    [Page 7]