Subject: Re: [Sip] Summarization of Reason header discussion

From: "Vijay K. Gurbani" <[email-masked]>
Date: Mon, 01 Apr 2002 09:21:09 -0600

Rohan Mahy wrote:

> Hi Folks,
> 
> I haven't heard anything more about the Reason header discussion, so I'm
> going to summarize what I think we have consensus on.
[...]

Rohan:

I listed this before as well, but once again, the I-D says that the
header can appear in any request or response.  IMHO, it can appear
in any request, but should be limited to some responses.  There was
some email exchange between me, Sean Olson, and Tom Taylor, which
resulted in 155 and 183 being possible responses where the header
adds some value.

> 3) From a syntax perspective, I think we got agreement that the Reason
> should always begin with a SIP response code and a textual phrase, but may
> also include other responses/code families as extra parameters (for
> example, CPIM error messages, Q.850 error codes, etc.).  The motivation is
> that a SIP device only needs to know about one set of response codes (SIP)
> to do something appropriate with the Reason, but additional information is
> available if you care.
> 
> So, I'd like to find out if folks agree that my summary is accurate, and
> if we can move forward on defining a Reason header in SIP.

One more question, if the Reason header always begins with a response
code, can it appear in a request that initiates a dialog -- since there
is no response to pass through in this case.  This is more of case 5
Gonzalo identified in
http://www1.ietf.org/mail-archive/working-groups/sip/current/msg04410.html
I re-read that again and am not quite sure if Reason is applicable in
instances where a dialog has not been established.  For example, when a
B2BUA invites the second leg of a 2-party call, what Reason header
will it carry in the initial INVITE towards that leg?

Regards,

- vijay
-- 
Vijay K. Gurbani  vkg@{lucent.com,research.bell-labs.com,acm.org}
Internet Software and eServices Group
Lucent Technologies/Bell Labs Innovations, 2000 Lucent Lane, Rm 6G-440
Naperville, Illinois 60566     Voice: +1 630 224 0216

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---

From: "Bob Penfield" <[email-masked]>
Date: Wed, 3 Apr 2002 08:58:18 -0500

see below
----- Original Message -----
From: "Rohan Mahy" <[email-masked]>
> 1) Gonzalo sent a bunch of requirements.  Nobody fundamentally challenges
> that the requirements are wrong or unimportant.  We've also seen a few
> proposed additions.  Lots of interesting stuff could reference this work.
>
> 2) Dave Oran proposed that we keep a split between the reason a call
> arrived, and the request history (which contains names).  The later has
> lots of privacy concerns, while the privacy concerns for the former are
> minimal.  I didn't see much in the way of objections here.
>

I think all we need is 3 elements: a type (SIP, CPIM, Q.850, etc), a status
code, and a reason phrase. If an element does not know the type, it just
ignores it. It seems wasteful to have to make up and include a SIP status
code when all I want to do is pass the ISUP cause code. I also think we
should allow multiple Reason headers in case we have multiple types of
status codes.

cheers,
(-:bob