Subject: [Sip] Updated route construct specification

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 17 Oct 2006 16:01:01 -0400

I've updated this document. It is (once again) almost completely 
rewritten. Until it appears in the archives, you can pick it up at:

http://www.jdrosen.net/papers/draft-rosenberg-sip-route-construct-02.txt

Basically, it proposes to turn Service-Route into the inverse of Path, 
so that Service-Route/Path work more like record-routing. This is now 
specified in a way which is backwards compatible with IMS, which was an 
issue for the previous spec. I believe this makes service-route usable 
for the internet at large, and it is a key part of solving the 
sip-outbound mid-dialog failover problem. Its also WAY simpler than 
previous versions. The whole bit in there about redirections overriding 
route sets is now folded into the more general UA loose routing document 
I also published.

Just to get some controversy thrown in there, the draft also specifies 
as part of its behavior that a UA register only a single contact at a 
time, and only that contact get reflected in the REGISTER response.

Thanks,
Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Cisco Fellow                                   Parsippany, NJ 07054-2711
Cisco Systems
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---

From: Marc Petit-Huguenin <[email-masked]>
Date: Fri, 27 Oct 2006 17:35:51 -0700

Hi Jonathan,

It seems that the text for the 305 response disappeared between -01 and
-02, but draft-rosenberg-sip-outbound-discovery-mid-dialog-00 is still
using this reference.  Is there a plan to move the 305 text to another I-D?

Thanks.

-- 
Marc Petit-Huguenin           [                                 ]
Home: [email-masked] [ RFC1855-compliant space for rent]
Work: [email-masked]            [                                 ]

---

From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Mon, 30 Oct 2006 18:34:52 +0100

Hi,

Thank you for putting this document together! Some initial comments and
questions.

My FIRST comment/question is: do we really need the "p2sr" flag? Isn't
it enough that, if the UA includes the "sr" flag, that the registrar
simply generates the Service-Route based on the Path and return it to
the UA?

My SECOND comment/question is on the "table" on page 9. In rows 2, 3 and
5 it is indicated that the new SR procedures are used, ie the
Service-Route should override the outbound proxy in the UA. Now, in an
IMS scenario P1 could be a P-CSCF, and if it doesn't insert the "p2sr"
it would not receive the initial requests. Or, have I missunderstood?

My THIRD comment/question is on the statement in chapter 2.3. The text
says:

"RFC 3261 is also clear that the resulting route set applies to
mid-dialog requests.  It
implies (though does not explicitly say) that the resulting route set
overrides any default outbound proxies (which represent a pre-loaded
route set)."

I don't think this is "clear" at all, and from my interop experience the
does-the-outbound-proxy-apply-to-mid-dialog-requests question comes up
quite often. And, just a couple of weeks ago I was informed about a
Cisco phone sending BYE to the outbound proxy, instead of using the
route set, so... ;)

My FOURTH comment/question is on the statement in chapter 6.1, saying
that the Service-Route is recomputed for each registration. I think it
would be good to mention that in that sense the Service-Route is
DIFFERENT from Record-Route/Route, which is not recomputed (e.g. using
re-INVITE/UPDATE) once it has been created. Only the remote/local target
can be changed.

Regards,

Christer

> -----Original Message-----
> From: Jonathan Rosenberg [mailto:[email-masked]] 
> Sent: 17. lokakuuta 2006 23:01
> To: IETF SIP List
> Subject: [Sip] Updated route construct specification
> 
> I've updated this document. It is (once again) almost 
> completely rewritten. Until it appears in the archives, you 
> can pick it up at:
> 
> Basically, it proposes to turn Service-Route into the inverse 
> of Path, so that Service-Route/Path work more like 
> record-routing. This is now specified in a way which is 
> backwards compatible with IMS, which was an issue for the 
> previous spec. I believe this makes service-route usable for 
> the internet at large, and it is a key part of solving the 
> sip-outbound mid-dialog failover problem. Its also WAY 
> simpler than previous versions. The whole bit in there about 
> redirections overriding route sets is now folded into the 
> more general UA loose routing document I also published.
> 
> Just to get some controversy thrown in there, the draft also 
> specifies as part of its behavior that a UA register only a 
> single contact at a time, and only that contact get reflected 
> in the REGISTER response.
> 
> Thanks,
> Jonathan R.
> -- 
> This list is for NEW development of the core SIP Protocol Use 
> [email-masked] for questions on current sip

---

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 31 Oct 2006 13:18:46 -0500

Yes. Sorry this was confusing; it was a consequence of the -00 vs non-00 
deadlines, and things changed in my documents between.

The whole bit about 305 moved into the loose-routing document:
http://www.ietf.org/internet-drafts/draft-rosenberg-sip-ua-loose-route-00.txt

and was vastly simplified. In that document, its not a specific response 
code any more that triggers the behavior. The complicated feature on 
targeting a redirect to a specific upstream client was removed. Its much 
simpler now.

-Jonathan R.

---

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 31 Oct 2006 13:27:49 -0500

> simply generates the Service-Route based on the Path and return it to

No. We need to know whether the proxies that inserted Path support this. 
  Otherwise, they will get requests from a UA that include a Route 
header that they are not expecting.

> Service-Route should override the outbound proxy in the UA.

This is a bug in the spec. Sorry about that. In cases 2,3 and 5 the 
registrar would compute the service-route from the Path, HOWEVER it will 
not include the "sr" option tag in the response. This puts the UA in 
'augment' mode, so that the service-route is added to the outbound proxy 
  list in the UA.

  Now, in an
> it would not receive the initial requests. Or, have I missunderstood?

Per above, my error. In the IMS scenario where the visited network 
doesn't support this, the UA would keep its outbound proxy and use Route 
ontop of that.

> Cisco phone sending BYE to the outbound proxy, instead of using the

Well, I think its clear that the RR applies to mid-dialog requests. 
Whats not clear is outbound proxies. THis spec is tryign to make that 
crystal clear.

> re-INVITE/UPDATE) once it has been created. Only the remote/local target

OK.

Thanks,
Jonathan R.

---

From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Tue, 31 Oct 2006 20:23:05 +0100

Hi Jonathan, 

>>My FIRST comment/question is: do we really need the "p2sr" 
>>flag? Isn't it enough that, if the UA includes the "sr" flag, that the

>>registrar simply generates the Service-Route based on the Path and 
>>return it to the UA?
> 
>No. We need to know whether the proxies that inserted Path 
>support this. Otherwise, they will get requests from a UA that include
a 
>Route header that they are not expecting.

That can happen already today, because those proxies cannot prevent the
registrar from inserting a Service-Route pointing towards them (which I
belive is fully allowed).

Regards,

Christer