Hello 

To use one registration policy for all kind of feature tags may be a
"one size fits all" policy that in my view can lead to unnecessary
bottlenecks and delays. Personally I find it useful how RFC 2506
describe various mechanisms for registration of feature tags, and think
the current approach where a feature tag can be specified within one
organization and subsequently registered by IANA works well and is a
useful approach. At least it worked well for the first tags... 

Similar ergistration is also performed for other parameters from IANA,
and 3GPP has also "registration procedures" with other organizations as
GSMA, TISPAN and OMA for various other parameters as well. In some cases
the registration is made by 3GPP and in some cases the registration is
made by other organisations. Who act as registrar depends on who "owns"
the basic functionality of the parameter. Technical discussions are
often held to find a solution, but when the technical discussions are
held and a solution is chosen, the registration process is done to
register and not to re-open the discussion. 

3GPP has three feature tags described in 3GPP specifications and
registered in the global tree and three more feature tags described in
3GPP specifications waiting for similar registrations by IANA. It might
be useful to distinguish between the possible need for changing the
process for registration of future tags and performing registration of
tags that are in operation only missing the formal registration. I would
assume that the current process is in operation until a new registration
policy is available and agreed.


Regards
Atle Monrad 
3GPP CT1 Chairman
______

Atle Monrad
Standardisation

ST-Ericsson
Product Group Mobile Platforms
 
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-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Gonzalo Camarillo
Sent: 20. mars 2009 11:47
To: sip
Subject: [Sip] Policy to register media feature tags

Folks,

as you know, RFC 3840 specifies how to indicate UA's capabilities using
media feature tags. Section 12.1 of RFC 3840 creates the SIP Media
Feature Tag Registration Tree. Media feature tags applicable to SIP are
registered in this tree.

http://www.ietf.org/rfc/rfc3840.txt

RFC 2506 defines the global tree to register feature tags. Section 3.1.2
of RFC 2506 says: "A registration may be proposed for the global tree by
anyone who has the need to allow for communication on a particular
capability or preference".

http://www.ietf.org/rfc/rfc2506.txt

The currently registered feature tags in both the SIP and the global
trees can be found at:

http://www.iana.org/assignments/media-feature-tags

As you can see, the only three feature tags registered in the global
tree come from 3GPP.

The issue we are facing is that the SIP and the global trees have
different registration policies. The SIP registry requires an RFC
defining the feature tag while the global tree only requires an expert
review.

Now, 3GPP would like to register two new feature tags:  g.3gpp.icsi-ref,
g.3gpp.iari-ref

This is the description of how these feature tags will be used:

"Each value of the Application Reference media feature-tag indicates the
software applications supported by the agent. The values for this tag
equal the IMS communication Service Identifier (ICSI) and IMS
Application Reference Identifier (IARI) values supported by the agent.
The Application Reference media feature tag is defined to fulfil the
requirements for forking to an appropriate UE when multiple UEs are
registered and dispatch to an appropriate application within the UE
based upon the IMS communication Service Identifier
(ICSI) and IMS Application Reference Identifier (IARI) values as stated
in 3GPP TS 23.228.  Multiple tag-values can be included in the
Application Reference media feature-tag."


The expert reviewer indicated that this tags will not contain simple
features but rather more complex services, or feature sets, or
application logic (pick your favorite term). Therefore, he did not find
it appropriate to register them in the global tree. He suggested that
RFC 2506 is amended so that it covers this type of more complex
features.

However, before going down that path, I would like to get comments from
the SIP community. The underlying issue is that we need to decide which
policy we want to apply to these types of registrations in SIP.

1) We decide that an RFC is always needed. Then, we can just use the SIP
registry. We would probably need to clarify or to stress somewhere that
the global tree is not appropriate for SIP tags.

2) We decide that an expert review is good enough. Then we would
probably need to amend RFC 2506 or RFC 3840 to reflect this.

Comments are welcome.

Thanks,

Gonzalo

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