H.323 Uniform Resource Locator (URL) Scheme Registration
RFC 3508

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Network Working Group                                           O. Levin
Request for Comments: 3508                                     RADVISION
Category: Informational                                       April 2003

        H.323 Uniform Resource Locator (URL) Scheme Registration

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   ITU-T Recommendation H.323 version 4 introduced an H.323-specific
   Uniform Resource Locator (URL).  This document reproduces the H323-
   URL definition found in H.323, and is published as an RFC for ease of
   access and registration with the Internet Assigned Numbers Authority
   (IANA).

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 BCP 14, RFC 2119 [2].

Table of Contents

   1. Introduction...................................................2
   2. URL Scheme Formal Syntax Definition and Character Encoding.....2
   3. Intended Usage.................................................3
   4. Applications and/or protocols, which may use H.323 URL scheme..3
   5. Security Considerations........................................3
   6. IANA Considerations............................................4
   References........................................................4
   Acknowledgments...................................................5
   Author's Address..................................................5
   Full Copyright Statement..........................................6

Levin                        Informational                      [Page 1]
RFC 3508                    H.323 URL Scheme                  April 2003

1.   Introduction

   ITU-T Recommendations H.323 [3] and H.225.0 [4] define a system for
   multimedia communications services over packet based networks.
   H.225.0 [4] defines an alias type for carrying any standard Uniform
   Resource Locator (URL).  H.323 version 4 [3] introduced an H.323-
   specific URL, which may be used to resolve the address of a network
   entity to which H.323 calls may be directed.

   This document reproduces the H323-URL definition found in ITU-T
   recommendation H.323 [3] and is published as an RFC for ease of
   access and IANA registration.

2.   URL Scheme Formal Syntax Definition and Character Encoding

   The H.323 URL is defined in ABNF as shown below.  Note that it
   utilizes the Core Rules specified in section 6.1 of [2].

   H323-URL    =   "h323:" address [ url-parameters ]
   address     =   user / "@" hostport / user "@" hostport
   user        =   1*(%x21-24 / %x26-3F / %x41-7F / escaped)
                        ; The symbols "%", "@", and symbols with
                        ; a character value below 0x21 may be
                        ; represented as escaped sequences.
   hostport    =   host [ ":" port]
   host        =   hostname / IPv4address / IPv6reference
   hostname    =   *( domainlabel "." ) toplabel [ "." ]
   domainlabel =   alphanum / alphanum *( alphanum / "-" ) alphanum
   toplabel    =   ALPHA / ALPHA *( alphanum / "-" ) alphanum
   IPv4address =   1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT
   IPv6reference   =  "[" IPv6address "]"
   IPV6address =   hexpart [ ":" IPv4address ]
   hexpart     =   hexseq / hexseq "::" [ hexseq ] / "::" [ hexseq ]
   hexseq      =   hex4 *( ":" hex4 )
   hex4        =   1*4HEXDIG
   port        =   1*DIGIT
   url-parameters  =   *( ";" url-parameter )
   url-parameter   =   1*(%x21-24 / %x26-3A / %x3C-7F / escaped)
                          ; Specific parameter definitions are for
                          ; further study.
                          ; The symbols "%", ";", and symbols
                          ; with a character value below 0x21 may be
                          ; represented as escaped sequences.
   alphanum    =   ALPHA / DIGIT
   escaped     =   "%" HEXDIG HEXDIG

   The host is case insensitive.

Levin                        Informational                      [Page 2]
RFC 3508                    H.323 URL Scheme                  April 2003

   The "user" is a Unicode [8] string that shall be UTF-8 [7] encoded
   and then escaped as necessary.  In the "user" field, the characters
   with a numeric value below 0x80 are case insensitive and the
   characters with a numeric value above or equal to 0x80 are case
   sensitive.

   The character set and case sensitivity of the "url-parameter" is
   specified in each parameter definition.

3.   Intended Usage

   The H.323 URL is intended to help an entity resolve the address of
   another H.323 entity, where an "entity" may be a user, a device, or a
   service.  The "user" portion of the URL specifies an alias for the