RFC 3508 (rfc3508) - Page 2 of 6

H

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