Subject: [Sipping] More discussion of service-route draft

From: "Dean Willis" <[email-masked]>
Date: Tue, 20 Nov 2001 15:47:24 -0600

The service-route draft:

http://search.ietf.org/internet-drafts/draft-bjorkner-sip-serviceroute-00.tx
t

is a fairly complete writeup of one of the two loose-routing approaches we
came up with during the ad-hoc in London. The other suggestion from London
was a loose/strict modifiers on routes in the Route header, and there was an
older suggestion (from Alan Johnston) on using an maddr parameter on the
original request-URI.

"loose routing", as you may recall, is an attempt to meet the requirement of
delivering outbound services from a non-local proxy. For example, if I have
aspeed-dial service on my home proxy, I woulsd add the home proxy to my
servcie routem then send the request to my local outbound proxy. Before the
request gets delivered to the destination UA, it gets passed through my home
proxy, which might do something useful with it.

Anyhow, I think that there is a fairly clear path to using the service-route
proposal to meet the "how to get outbound services from the  home proxy"
requirement posed by 3GPP. In fact, I think it's a complete solution (or at
least very close) to that problem. There's the seperate problem of "how do I
find out what my home proxy is" that will have to be solved, but there are
three or four easy ways to do that and we've declared that a seperate
problem.

SO-- if you're involved in the 3GPP requirements work, please review the
afore mentioned draft, and if you either disagree with my "it's a fix"
assertion or wish to discuss it further, please do so. Also, please look it
over if you see a need to get outbound services from a home proxy in any
other sort of network (and I know you Comm/ASP people have this problem).

If this really does appar to be an effective solution, we can recommend it
up the the SIP group for detail consideration and implementation.

Thanks,

--
Dean Willis

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---

From: "Sean Olson (EUS)" <[email-masked]>
Date: Tue, 27 Nov 2001 17:54:34 -0600

Hi,

I glad to see this issue brought up again. Hopefully
we can lay this one to rest soon. Here are some 
immediate comments to the proposal:

1) Insertion of the Proxy-Require: seems like a bad
   idea and seems to violate the notion of a loose
   route. I think it should be possible to have
   proxies on the path between entries in the Service-Route:
   list that know nothing about the Service-Route: header.
   Proxy-Require: violates this. I don't see a real problem
   with removing the Proxy-Require: altogether.

2) In the case where both Service-Route: and Route: headers
   are present, the property that a proxy is able to manipulate
   the Request-URI independently of the "route" is lost. Shouldn't
   a 4xx be returned in this scenario by the first proxy that
   understands the Service-Route: header? The interaction should
   be spelled out more clearly here.

This mechanism cleans up some of the problems with a partial strict 
Route: established via the Path: header extension. It is superior in
that respect. However, this does not address the problem of routing a 
request to the "terminating" proxy in the visited network. The Path: header
defines a bi-directional path that the Service-Route: header does not. 
I hope that at the end of this discussion that we can come up with a single
extension and not rely on a mixture of Path: and Service-Route:. This would
be two steps backward.

Regards,
Sean Olson
Ericsson Inc.