Subject: [Sip] substantive changes to outbound

From: "Rohan Mahy" <[email-masked]>
Date: Fri, 29 Feb 2008 14:38:56 -0800

Hi Folks,

As many of you probably saw, I submitted a new version of the outbound
specification just before the draft deadline on Monday. There was a lot of
general rewording to try to improve clarity and readability, but we received
a number of contradictory suggestions, so hopefully it flow well.  The major
changes are:

- removed references to the 'keep' and 'timed-keepalives' parameters
- added the 'Flow-Timer' header
- changed the wording for the recommended timing over TCP. if battery
consumption is an issue, the recommended keepalives are approximately every
14 minutes.  If battery consumption is not an issue, the recommended
keepalives are approximately every two minutes.
- added text explaining that an edge proxy which sees an 'ob' parameter in
its Route header (probably copied form the Path vector by the authoritative
proxy) in a dialog-forming request, the edge proxy needs to insure that the
route set will allow in-dialog requests to arrive over some valid flow to
the UA instance. In the simplest cae, the edge proxy could just copy the URI
(with flow token) from the Route header into the Record-Route header and
delete the 'ob' parameter. If the Contact is a GRUU that should be
sufficient too.  If the edge proxy wants to do something fancy that even
without GRUU allows mid-dialog recovery of a specific flow, that's allowed
as well.
- added the 439 (First Hop Lacks Outbound Support) response code
- wrote a very complete example (which is hopefully correct)

I hope this is satisfactory to the group. The way timers work is much
simpler and more powerful and will hopefully please both server and client
folks (wired and wireless alike).

In addition, there was a comment on the list about using outbound with
transaction stateless proxies.  As it turns out, it is impossible to
implement an RFC3261-compliant proxy that always operates statelessly.
Implementation of TCP (and TLS over TCP) is required in RFC 3261 and when
sending or receiving over TCP a proxy MUST become stateful. Based on this, I
do not feel badly stating that proxies which implement outbound MUST be
transaction stateful.

thanks,
-rohan
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From: "Francois Audet" <[email-masked]>
Date: Fri, 29 Feb 2008 19:12:17 -0600

When I went through the list of comments relating to draft-ietf-sip-outbound-11
in preparation for draft-ietf-sip-outbound-12, there was one item I agreed
with Rohan and Cullen that I would bring to the list. 

There were some questions raised about the usefulness of the Flow-Timer
parameter. Interestingly enough, it appears that this originally came from... myself.

While I remember why I originally tought it would be useful, I no longuer believe 
that it is useful.

My suggestion would therefore to remove the Flow-Timer parameter altogether.
(I will note that previous versions of the draft didn't have it).

Comments?

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From: Cullen Jennings <[email-masked]>
Date: Fri, 29 Feb 2008 17:40:08 -0800

> While I remember why I originally tought it would be useful, I no  

When you first suggested it, I was not in favor of it. But you  
convinced me over time that it was great. Now I love it.

Seriously, I don't feel strongly one way or the other. If no one wants  
it and is going to use it, I think we should remove it in the name of  
simplifying the draft.

Cullen <in my individual contributor role>