Re: [straw] FW: New Version Notification for draft-ram-straw-b2bua-feature-tag-00.txt

Hi Paul,

Sorry for delay. See inline

-----Original Message-----
From: straw <straw-bounces@ietf.org> on behalf of Paul Kyzivat
<pkyzivat@alum.mit.edu>
Date: Monday, 6 July 2015 6:47 pm
To: "straw@ietf.org" <straw@ietf.org>
Subject: Re: [straw] FW: New Version Notification for
draft-ram-straw-b2bua-feature-tag-00.txt

>Ram,
>
>I am puzzled by this. I can't figure out when/how it would be used, or
>if/how it relates to RFC6809 (proxy-feature).
>
>My problem is fundamentally whether the devices carrying this tag are to
>be viewed as endpoints or intermediaries.

These devices are primarily intermediary devices [ B2BUAs of types in RFC
7092].

> For the properties being
>described to be useful, I think one must view the device as an
>intermediary, that is somehow masking/modifying the intrinsic properties
>of the *actual* endpoint. Yet feature tags (callee capabilities) should
>be viewed as describing the target of communication.

Agree. Initially I had looked at RFC 3840 capabilities (some of them like
isFocus which is a special case of middle box terminating sessions) and
thought 3840 would fit in to indicate the B2BUA capabilities. After
reading RFC 6809 I think that is more relevant and each B2BUA in the path
can add a fci header with its type and so when the UA receives the INVITE
it will see the list of fci headers with the top most being the closest to
UA receiving the message.

The goal of this draft is for a UA to know the different types of B2BUA [
with in the scope of RFC 7092 types] between itself and the destination.
What the UA does by looking at the type of B2BUA is not in scope here.

Ram
>
>RFC6809 provides a way of describing properties of intermediaries on the
>signaling (and potentially also the media) path. Perhaps this new
>property belongs there instead.
>
>Another way to use a B2BUA is for me, as a user, to use a B2BUA as a
>foundation to build a virtual user agent, composed of one or more other
>UAs. That seems to fit your model. But in that case, other UAs
>interacting with it don't need to know that it is a B2BUA. Rather, they
>only need to know what capabilities it presents to the world. The fact
>that it is a B2BUA is simply an implementation detail.
>
>	Thanks,
>	Paul
>
>On 7/6/15 12:07 PM, Ram Mohan R (rmohanr) wrote:
>> Hi All,
>>
>>   We have published a new draft that extends the User Agent capabilities
>> specification(RFC 3840) to allow
>>     indication of Back-to-Back User Agent (B2BUA) types.
>> The motivation for this draft came out  of IESG review and subsequent
>> discussions of [I-D.ietf-straw-b2bua-stun] where it was pointed
>> that there is no existing mechanisms for B2BUA to indicate its presence
>> except for special cases like Focus.
>>
>> Please review and provide your inputs.
>>
>> Regards,
>> Authors
>>
>> -----Original Message-----
>> From: "internet-drafts@ietf.org" <internet-drafts@ietf.org>
>> Date: Monday, 6 July 2015 8:08 pm
>> To: Cisco Employee <rmohanr@cisco.com>, "Tirumaleswar Reddy (tireddy)"
>> <tireddy@cisco.com>, "Gonzalo Salgueiro (gsalguei)"
>><gsalguei@cisco.com>,
>> "Gonzalo Salgueiro (gsalguei)" <gsalguei@cisco.com>, "Tirumaleswar Reddy
>> (tireddy)" <tireddy@cisco.com>, Cisco Employee <rmohanr@cisco.com>
>> Subject: New Version Notification for
>> draft-ram-straw-b2bua-feature-tag-00.txt
>>
>>>
>>> A new version of I-D, draft-ram-straw-b2bua-feature-tag-00.txt
>>> has been successfully submitted by Ram Mohan Ravindranath and posted to
>>> the
>>> IETF repository.
>>>
>>> Name:		draft-ram-straw-b2bua-feature-tag
>>> Revision:	00
>>> Title:		A Session Initiation Protocol (SIP) Feature Tag for
>>>Back-to-Back
>>> User Agents (B2BUAs)
>>> Document date:	2015-07-06
>>> Group:		Individual Submission
>>> Pages:		8
>>> URL:
>>> 
>>>https://www.ietf.org/internet-drafts/draft-ram-straw-b2bua-feature-tag-0
>>>0.
>>> txt
>>> Status:
>>> https://datatracker.ietf.org/doc/draft-ram-straw-b2bua-feature-tag/
>>> Htmlized:
>>> https://tools.ietf.org/html/draft-ram-straw-b2bua-feature-tag-00
>>>
>>>
>>> Abstract:
>>>    The User Agent capabilities specification allows Session Initiation
>>>    Protocol (SIP) User Agents to convey their capabilities and
>>>    characteristics to other User Agents and to the registrar for its
>>>    domain.  This information is conveyed as parameters of the Contact
>>>    header field.  Amongst those capabilities are the type of User Agent
>>>    that is available at a SIP Uniform Resource Identifier (URI).  This
>>>    document extends the User Agent capabilities specification to allow
>>>    indication of Back-to-Back User Agent (B2BUA) types.
>>>
>>>
>>>
>>>
>>>
>>> Please note that it may take a couple of minutes from the time of
>>> submission
>>> until the htmlized version and diff are available at tools.ietf.org.
>>>
>>> The IETF Secretariat
>>>
>>
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