Subject: RE: [SIP] RECORD-ROUTE/ROUTE requirements

From: "Fairlie-Cuninghame, Robert" <[email-masked]>
Date: Thu, 30 Nov 2000 20:48:38 -0800

> 
> I don't think that proxies should start second-guessing UAS.
> I would say that the simplest thing is just to say that when the
> UA is building the Route header list, it should append the
> Contact, if present; failing that, the From.
> 
> Really old UAs might lose, but they were always going to do
> that, anyway[0].
> 
What about in the other direction? The UAC will need to add a Record-Route
for the _original_ Request-URI - which may in fact be entirely unhelpful. If
the proxy were to add the extra Record-Route I think that is much safer as
it knows what its own behaviour will be when it receives the request..

I guess, I was also trying to stick with the existing RFC2543 and bis UA
behaviour (minus route mangling). Ie, the UA doesn't add an extra
Route-Header for the original From or Request-URI - its only added if there
is a Contact (which I think is a good thing !!). 

I think we can do better than saying RFC2543 doesn't work. 

- If a proxy inserts Record-Route header into a request without neither a
Contact nor Record-Route header, then the Proxy MAY add a second
Record-Route header to the end of the R-R list using the From URL address
with the source address as an maddr parameter.

- If a proxy receives a response to a request in which it added a
Record-Route header AND the response does not contain a COntact header AND
no new headers have been added by other proxies (ie proxy is final
Record-Route'd proxy), then the proxy MAY add another preceeding
Record-Route header to the start of the response's R-R list using the
request's request-URI with the request's forward address as an maddr
parameter.

This should cover the majority of RFC2543 scenarios without too much fuss
for the proxy or UA - I think it is better than trying to embed using r-r
parameters as this just gets messya nd brittle. As I said before, I think it
is better that the proxy does this as it understand that it will use the
added Record-Route. If the UA tries this, it has little chance of success. A
UA has never (if I remember correctly) added extra R-R headers if there is
no Contact (and shouldn't matter even if it did).

What do you think ?

Robert.

_______________________________________________
SIP mailing list
[email-masked]
http://lists.bell-labs.com/mailman/listinfo/sip