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Network Working Group                                           O. LevinRequest for Comments: 3508                                     RADVISIONCategory: Informational                                       April 2003H.323 Uniform Resource Locator (URL) Scheme RegistrationStatus 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 inBCP 14,RFC 2119 [2].Table of Contents1. Introduction...................................................22. URL Scheme Formal Syntax Definition and Character Encoding.....23. Intended Usage.................................................34. Applications and/or protocols, which may use H.323 URL scheme..35. Security Considerations........................................36. IANA Considerations............................................4   References........................................................4   Acknowledgments...................................................5   Author's Address..................................................5   Full Copyright Statement..........................................6Levin                        Informational                      [Page 1]

RFC 3508                    H.323 URL Scheme                  April 20031.   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   entity, without carrying any information about the location of the   entity.  The "hostport", on the other hand, is the domain name of an   Endpoint, Gatekeeper, Border Element, or other functional element to   which H.323 calls may be directed or for which services may be   performed.4.   Applications and/or protocols, which may use H.323 URL scheme   H.323 URLs may be carried by other protocols, such as SIP [6] or TRIP   [9].  H.323 URLs may be also contained within web pages or within XML   data, which may be utilized by H.323 entities in order to initiate   calls or perform services.5.   Security Considerations   When an H.323 URL is carried within H.225.0 [4] messages, security is   addressed by the H.235 security framework [5].  When an H.323 URL   carried within other protocols (such as SIP [6]), the security is   addressed within the corresponding protocol.   In general, security, as it relates to the usage and carriage of the   H.323 URLs, is considered as an issue that should be addressed within   scope of H.323 or other relevant protocols and is not within the   scope of this document.Levin                        Informational                      [Page 3]

RFC 3508                    H.323 URL Scheme                  April 20036.   IANA Considerations   The purpose of this document is serving as a reference point for the   purposes of registering the H.323 URL scheme with IANA.   Having the URL registered with IANA will ensure that there is no   duplication of the URL scheme "h323".  This document reproduces the   exact H323-URL definition as published in ITU-T Recommendation H.323   [3].   Registration Template      URL scheme name: h323      URL scheme syntax:Section 2 of RFC 3508      Character encoding considerations:Section 2 of RFC 3508      Intended usage:Section 3 of RFC 3508      Applications and/or protocols which use this scheme:Section 4 of      RFC 3508      Interoperability considerations: None.  (Section 2 of RFC 3508      contains the first version of "h323" URL definition.)      Security considerations:Section 5 of RFC 3508      Relevant publications: [3] and [4]      Contact: Orit Levin, orit@radvision.com      Author/Change Controller: IESGReferences   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement        Levels",BCP 14,RFC 2119, March 1997.   [2]  Crocker, D., Editor, and P. Overell "Augmented BNF for Syntax        Specifications: ABNF",RFC 2234, November 1997.   [3]  ITU-T Recommendation H.323v.4 "Packet-based multimedia        communications systems", November 2000.   [4]  ITU-T Recommendation H.225.0 "Call signalling protocols and        media stream packetization for packet-based multimedia        communication systems", November 2000.Levin                        Informational                      [Page 4]

RFC 3508                    H.323 URL Scheme                  April 2003   [5]  ITU-T Recommendation H.235 "Security and Encryption for H Series        (H.323 and other H.245 based) multimedia terminals", November        2000.   [6]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,        Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:        Session Initiation Protocol",RFC 3261, June 2002.   [7]  Yergeau, F., "UTF-8, a transformation format of ISO 10646",RFC2279, January 1998.   [8]  ISO/IEC 10646-1:1993, Information technology "Universal        Multiple-Octet Coded Character Set (USC)" Part 1: Architecture        and Basic Multilingual Plane.   [9]  Rosenberg, J., Salama, H. and M. Squire, "Telephony Routing over        IP (TRIP)",RFC 3219, January 2002.Acknowledgments   This document is prepared and posted on behalf of SG-16 ITU-T.  I   wish to thank Paul E. Jones, Robert Callaghan and Cullen Jennings for   their comments and active help.Author's Address   Orit Levin   RADVISION   266 Harristown Road   Glen Rock, NJ USA   Phone:  +1-201-689-6330   EMail:  orit@radvision.comLevin                        Informational                      [Page 5]

RFC 3508                    H.323 URL Scheme                  April 2003Full Copyright Statement   Copyright (C) The Internet Society (2003).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Levin                        Informational                      [Page 6]