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Internet Engineering Task Force (IETF)                       D. CridlandRequest for Comments: 6075                                 Isode LimitedUpdates:2244                                              December 2010Category: Standards TrackISSN: 2070-1721The Internet Assigned Number Authority (IANA) Application Configuration            Access Protocol (ACAP) Vendor Subtrees RegistryAbstract   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 inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://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 toBCP 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 2010Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .22.  Conventions Used in This Document . . . . . . . . . . . . . . .23.  The Vendor Subtree Registry . . . . . . . . . . . . . . . . . .33.1.  Internationalization  . . . . . . . . . . . . . . . . . . .33.2.  Formal Syntax . . . . . . . . . . . . . . . . . . . . . . .43.3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . .43.4.  Changes fromRFC 2244 . . . . . . . . . . . . . . . . . . .54.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .54.1.  Example Registration  . . . . . . . . . . . . . . . . . . .65.  Security Considerations . . . . . . . . . . . . . . . . . . . .66.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . .67.  References  . . . . . . . . . . . . . . . . . . . . . . . . . .67.1.  Normative References  . . . . . . . . . . . . . . . . . . .67.2.  Informative References  . . . . . . . . . . . . . . . . . .71.  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 replacesSection7.4 and portions ofSection 4, particularlySection 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 inSection 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 inSection 3.2).Cridland                     Standards Track                    [Page 3]

RFC 6075              ACAP Vendor Subtrees Registry        December 20103.2.  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 20103.4.  Changes fromRFC 2244   This non-normative section details changes from the original   specification of the registry inRFC 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 20104.1.  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.  References7.1.  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 20107.2.  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.comCridland                     Standards Track                    [Page 7]