ITU Telecommunication Standardization Sector
Study Group 16
Q.F,G,K,2-5/16 Rapporteur Meeting
Beijing, 11-14 May 2004
Document AVD-2426
Question(s):
Q.2/16
Source*:
International Multimedia Telecommunications Consortium (IMTC)
Title:
IMTC UMMAP Recommendation A.1: Acceptable Addressing Formats
Purpose:
Liaison Statement
___________________
Attached is draft document ‘Recommendation A.1v0.4: Acceptable Addressing Formats’ that is
being developed within the IMTC Universal Multimedia Addressing Platform (UMMAP)
Activity Group (http://www.imtc.org/activity_groups/UMMAP.asp). This effort from IMTC is in
response to concern from the user community that the current state of deployed multimedia
conferencing networks are using addressing formats that are not compatible and that do not scale
universally. The purpose of the Recommendation is to provide assurance to system
manufacturers and end users that UMMAP A.1 compliant systems are in fact universally
addressable and scalable.
IMTC seeks comment from ITU-T SG 16 in the following areas:
1. Technical accuracy. Does the language adequately describe the desired functionality?
2. Scope. Is the problem properly articulated and does the solution address the stated goal?
3. Potential Standardization. IMTC recognizes that it is not a standards body but an
industry consortium, and is interested to know if this effort is seen as appropriate for
standardization within ITU-T.
4. Fit within NGN. Does this effort have a place within ITU’s NGN initiative?
___________________
* Contact:
Tyler Miller Johnson
University of North Carolina at Chapel Hill
CB# 3455
Chapel Hill, NC 27599
USA
Tel:
+1.919.843.7004
Fax:
+1.919.843.7008
E-mail: Tyler_Johnson@unc.edu
International Multimedia Telecommunications Consortium
Universal MultiMedia Addressing Platform (UMMAP)
Recommendation A.1: Acceptable Addressing Formats
Contents
Purpose and Scope ...................................................................................................2
Definitions................................................................................................................2
UMMAP Recommendation .....................................................................................3
Core Address Types ..............................................................................................3
H323 URL..........................................................................................................3
SIP URI ..............................................................................................................3
Tel URI ..............................................................................................................3
Gateway Dialing ...................................................................................................4
Conformance ............................................................................................................5
UMMAP Address Representation Conformance..................................................5
UMMAP Call Signaling Conformance .................................................................5
UMMAP User Input Conformance .......................................................................5
References ................................................................................................................5
Contact .....................................................................................................................5
Revision History ......................................................................................................6
Version number
0.1
0.2
0.3
0.4
Modifications
Original document
Draft sent to UMMAP list
Feedback provided during April 14 UMMAP meeting
Miscellaneous typographical and formatting changes
Date
April 2, 2004
April 12, 2004
April 20, 2004
April 22, 2004
International Multimedia Telecommunications Consortium
Purpose and Scope
The IMTC Universal Multimedia Addressing Platform (UMMAP) Recommendation A.1 defines
a set of addressing guidelines which ensure that any multimedia conferencing user or system can
be uniquely identified and signaled on the Internet. The overarching goal is that any user can be
reached at an address, regardless of the source or destination of the call, or the source,
destination or intermediate signaling protocols in use.
A key principle is that the developing global multimedia conferencing environment is
‘universal.’ This implies that multiple, autonomous networks must interoperate, and that their
numbers are sufficiently large and topologies so diverse that it is not practical (nor necessarily
desirable) to establish deliberate application level peering relationships among them. Instead,
conferencing systems must signal the underlying network for address resolution.
Drawing from existing standards, UMMAP Recommendation A.1 proscribes acceptable
addressing formats that can be used by multimedia conferencing systems to enable any user or
system to be contacted. In short, using systems conforming to UMMAP Recommendation A.1,
any user should be able to say, ‘Here is my address. Call me,’ and be assured that a call placed to
that address will connect. UMMAP does not proscribe protocol level or network level
functionality, but rather assumes that functionality to be already present.
Definitions
MUST – Required for compliance
SHOULD – Recommended, but not required for compliance
Recommendation A.1 – Acceptable Addressing Formats
v0.4 – April 22, 2004
IMTC UMMAP
Page 2 of 6
International Multimedia Telecommunications Consortium
UMMAP Recommendation
UMMAP allows several addressing types, including ENUM, H.323 URL, SIP URI and Tel URI.
UMMAP does not favor one of these types, but rather leaves it to the market and individual
implementations to choose which types to use and publish. For example, UMMAP does not
proscribe that all H.323 Internet systems have E.164 numbers reachable by ENUM. Instead, an
H.323 Internet system may have H.323 URLs and no corresponding E.164 address.
Core Address Types
H323 URL
H.323 defines a URL syntax for resolution of H.323 addresses using DNS. When an
address is represented in H.323 URL format, it SHOULD be resolved using a DNS
lookup as specified by ITU-T Recommendation H.323.
SIP URI
The Session Initiation Protocol (SIP) defines a URL syntax for resolution of SIP
addresses using DNS. When an address is represented in SIP URI, or SIPS URI format, it
SHOULD be resolved using a DNS lookup as specified by IETF RFC 3261.
Tel URI
The Tel URI defines a URI syntax for the representation of telephone numbers on the
Internet. Telephone numbers SHOULD be represented in Tel URI format as specified in
IETF RFC 2806. Additionally, modem numbers SHOULD be represented in Modem URI
format and fax numbers SHOULD be represented in Fax URI format, also specified in
RFC 2806.
ENUM defines a method for translating E.164 telephone numbers into Internet addresses
resolvable through DNS. When an address is represented in Tel URI format, it SHOULD
be resolved using a DNS lookup as specified by IETF RFC 2916.
When a Tel URI (or Fax or Modem) is not found in ENUM, the call controller should
either forward the call using a PSTN gateway, or return a ‘destination unreachable as
dialed’ message.
Recommendation A.1 – Acceptable Addressing Formats
v0.4 – April 22, 2004
IMTC UMMAP
Page 3 of 6
International Multimedia Telecommunications Consortium
Gateway Dialing
It is the responsibility of the system originating the call to present an address to the network
in the format of the target address. This is trivial when placing calls between systems using
the same protocol. When dialing between protocols, a gateway must be used, thus the system
initiating the call is responsible for indicating a gateway is necessary for call completion. For
example, if an H.323 system calls a SIP system, the H.323 system must be capable of
resolving the SIP URI and routing the call through an appropriate gateway. UMMAP does
not specify how that gateway is discovered or signaled. Thus, every UMMAP A.1 compliant
system MUST be capable of dialing every UMMAP Core Address Type.
The call controller must know about gateways available to translate between signaling
protocols based on the source device capabilities and the dialed destination URI.
Additionally, the call controller must be capable of routing the call thru any transcoding
systems necessary for content protocol conversion as necessary.
There is a need for a standard method to locate translational gateways and to learn their
capabilities, as none exists today.
Recommendation A.1 – Acceptable Addressing Formats
v0.4 – April 22, 2004
IMTC UMMAP
Page 4 of 6
International Multimedia Telecommunications Consortium
Conformance
UMMAP defines three forms of conformance: Address Representation, Call Signaling and User
Input.
UMMAP Address Representation Conformance
An address is said to be UMMAP Address Representation Conformant when it is
represented in one of the Core Address Types.
UMMAP Call Signaling Conformance
A system that is said to be UMMAP Call Signaling Conformant MUST be able to initiate
a call using one or more of the Core Address Types, and SHOULD be able to initiate a
call using any of the Core Address Types. For example, a system that can dial using
H.323 URL only must be able to send any Core Address Type to the call controller for
processing. A system that is said to be UMMAP Call Signaling Conformant MUST be
capable of receiving a call in the format in which its address is represented. For example,
an H.323 endpoint whose UMMAP Address Representation is h323:john@gk.domain
must be capable of receiving calls in H.323 URL format.
UMMAP User Input Conformance
An endpoint that is said to be UMMAP User Input Conformant MUST allow the user to
enter and store an address in ALL of the recommended Core Address Types in their
native syntax without embedding. UMMAP does not specify the method of user input,
but these methods might include keyboard entry, text entry via numeric dial pad, web
page, voice recognition, or selection through directory lookup.
References
- ITU-T Recommendation E.164 (1997), The international public telecommunication numbering plan. From
http://www.itu.int/rec/recommendation.asp?type=items&lang=E&parent=T-REC-E.164-199705-I
- ITU-T Recommendation H.323 (2000), Packet-based multimedia communications systems. From
http://www.itu.int/rec/recommendation.asp?type=folders&lang=e&parent=T-REC-H.323
- IETF RFC 3261 (2002), SIP: Session Initiation Protocol. From http://www.ietf.org/rfc/rfc3261.txt
- IETF RFC 2916 (2000), E.164 number and DNS (ENUM). From http://www.ietf.org/rfc/rfc2916.txt
- IETF RFC 2806 (2000), URLs for Telephone Calls. From http://www.ietf.org/rfc/rfc2806.txt (an update is
expected in 2004)
Contact
For questions or comments about this recommendation, contact the UMMAP Activity Group (details listed at
http://www.imtc.org/activity_groups/UMMAP.asp).
Recommendation A.1 – Acceptable Addressing Formats
v0.4 – April 22, 2004
IMTC UMMAP
Page 5 of 6
International Multimedia Telecommunications Consortium
Revision History
A.1v0.4:
-Changed
Contact information updated.
Fixed various spelling and syntax errors
A.1v0.3: April 20, 2004 – Edits based on UMMAP AG conference call 4/14/04 & editorial corrections
-Changed
‘Specification’ to ‘Recommendation’
Fixed various spelling and syntax errors
-Added
Modem and Fax URI to the Tel URI section under Core Address Types
Paragraph at the end of Core Address Types-Tel URI regarding what happens if the ENUM lookup fails
Paragraph to Gateway Dialling regarding signalling and protocol translation
Clarification under User Input Conformance regarding address entry and storage
Clarification under Call Signalling Conformance regarding embedding of URIs
URLs for all references
Revision History
A.1v0.2: April 9, 2004 – Named document ‘Specification A.1’
A.1v0.1: April 1, 2004 – Original document submitted by Tyler Johnson, UNC
Recommendation A.1 – Acceptable Addressing Formats
v0.4 – April 22, 2004
IMTC UMMAP
Page 6 of 6