One document matched: draft-levin-iptel-h323-url-scheme-01.txt

Differences from draft-levin-iptel-h323-url-scheme-00.txt

O. Levin
Internet Draft
RADVision

Document: draft-levin-iptel-h323-url-scheme-01.txt
November 2000
Category: Informational



			H.323 URL scheme definition


Status of this Memo

This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026 except that the right to produce
derivative works is not (automatically) granted.

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1. Abstract

H.323 Specification [3] and H.225.0 [4] together define a system and a
set of protocols for multimedia communications services over Packet
Based Networks (PBN).   H.225.0 [4] messages define means for carrying
any standard URL (Uniform Resource Locators) in order to specify source
and destination, involved in the call. Starting from H.323v.4, H.323
URL is defined in order to specify H.323 party involved in the call.
This H323-URL definition has a form of user@host where user corresponds
to endpoint's alias and host corresponds to its domain/zone/gatekeeper
(in terms of [3]).  The purpose of this document is to register the
specified (and presented below) H.323 URL scheme within IANA. This will
allow for improved resources use and integration over the Internet.


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 RFC-2119 [1].


3. URL scheme name

Taking into consideration the guidelines of RFC-2717[12], the proposal
is to register the H.323 URL scheme, named "H323", within the IETF
tree. It is despite the fact, that H.323 has been defined by ITU-T.
H.323 has been widely deployed today and is used side-by-side with
other Internet protocols and technologies. We would like to prevent the
segmentation of URL scheme definitions, belonging to the same group of
applications and running on the same Networks. In addition, it would allow for closer revision of the H323 scheme within the IETF community.


4. 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				=	%x21-x24 / %x26-x3F / %x41-FF / 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		=	%x21-x24 / %x26-x3A / %x3C-xFF / escaped
					; Specific parameter definitions are for further
					; study. 	The symbols "%", "@", and symbols with
					; a character value below 0x21 may be represented
					; as escaped sequences.

unreserved		=	alphanum / mark
alphanum			=	ALPHA / DIGIT
mark				=	"-" / "_" / "." / "!" / "~" / "*" / "'"
					/	"(" / ")" / "&" / "=" / "+" / "$" / ","
escaped			=	"%" HEXDIG HEXDIG

The H.323 URL is Case Insensitive.
The value user is a Unicode string encoded in UTF-8 [14].

5. Intended Usage


One of the alias types defined by H.323 [3] is the url-ID, which is intended to contain standard URL schemes that may be used to reach resources. In addition, URLs are referenced within Annex K/H.323 [13] and may be used in other services added to H.323 in the future. An H.323 entity may accept any valid URL that it understands, but should support the H.323 URL as defined in [3] and is reproduced in this document.
The H.323 URL is intended to help an entity resolve the address of another H.323 entity. It is composed of two parts: the user and the hostport. The user specifies an alias for the entity, such as a user or a service, without carrying any information about the location of the entity. The hostport, on the other hand, is the domain name of an Endpoint, Gatekeeper, or Border Element using terminology of [3].


6. Applications and/or protocols, which may use this URL scheme name

H.323 URL may be carried by another protocols, such as SIP [6]. It is practicable when the information about the destination (or the source) protocol is specified as a part of its URL. For example, that would facilitate SIP-H.323 interoperability (discussed in [7]) in more efficient manner.


7. Security Considerations

H.323 URL definition conceptually has the same approach as already defined and widely used other URL schemes, such as [7].  When H.323 URL is carried within H.225.0 [4] messages the security is addressed by H.323 Security framework [5]. When H.323 URL is carried within other protocols (such as SIP [6]), the security is addressed within the corresponding protocol.


8. References

1 Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels", BCP 14, RFC 2119, March 1997

2 Crocker, D. and Overell, P.(Editors), "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, Internet Mail Consortium and Demon
Internet Ltd., 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


5 ITU-T Recommendation H.235 "Security and Encryption for H Series
(H.323 and other H.245 based) multimedia terminals", November 2000


6 M. Handley, H. Schulzrinne, E. Schooler, and J. Rosenberg, "SIP:
session initiation protocol," Request for Comments (Proposed Standard)
2543, Internet Engineering Task Force, Mar. 1999



7 K. Singh and H. Schulzrinne,"Interworking Between SIP/SDP and H.323"
Internet Draft, May 2000



8 Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform resource
locators (URL)", RFC 1738, December 1994


9 Hoffman, P., Masinter, L. and J. Zawinski, "The mailto URL scheme",
RFC 2368, July 1998


10 Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform resource identifiers (URI): generic syntax", RFC 2396, August 1998



11 Crocker, D., "Standard for the format of ARPA internet text
messages", RFC STD 11, RFC 822, August 1982


12 R. Petke and I. King, "Registration Procedures for URL Scheme
Names", RFC 2717, BCP-35, November 1999


13 ITU-T Recommendation H.323 Annex K "HTTP based service Control
Transport Channel", May 2000

14 F. Yergeau, "UTF-8, a transformation format of ISO 10646", RFC 2279, January 1998


9. Acknowledgments

This document is prepared and posted on behalf of SG-16 ITU-T. I wish to thank this group of dedicated people and especially Paul E. Jones and Robert Callaghan for their invaluable comments and active help.


10. Author's Addresses

Orit Levin
RADVision Inc.,
575 Corporate Drive Suite 420
Mahwah, NJ 07430
Phone: +1 201 529 4300
Email: orit@radvision.com



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	H.323 URL scheme definition	November 2000



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