Subject: RE: [SIP] Outbound proxy (was: proxy routing logic)

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 1 Jan 2001 23:36:59 -0500

> -----Original Message-----
> From: Henning Schulzrinne [mailto:[email-masked]]
> Sent: Sunday, December 31, 2000 12:57 AM
> To: Billy Biggs
> Cc: [email-masked]
> Subject: Re: [SIP] Outbound proxy (was: proxy routing logic)
> 
> 
> In any event, the new text should clearly state what outbound proxies
> need to do with Route headers. The 'every host removes top Route' rule
> implied in 2543/6.33 would not work with outbound proxies, 
> since the UAC
> already removed the top Route and placed it in the Request-URI. (I
> scanned the new text and it seems silent on this issue at least in
> section 'proxy processing of non-initial request'.)

My concern is that a proxy may not know its an "outbound" proxy. Worse yet,
whether its "outbound" or not may vary from request to request, and I REALLY
don't want special rules at a proxy server depending on knowing such a piece
of information. The only entity that definitively knows whether its using an
outbound proxy is the UA which sends the request there. As such, it is my
strong preference that any special route processing for outbound proxies
take place in the UA, since it already needs to do something special anyway.
In your example, Henning, the UA could simply not strip the top Route header
when sending to its outbound proxy. That solves the problem.

-Jonathan R.

---
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.cs.columbia.edu/~jdrosen         PHONE: (973) 952-5000
http://www.dynamicsoft.com

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From: "Henning G. Schulzrinne" <[email-masked]>
Date: Tue, 02 Jan 2001 10:01:16 -0500

> when sending to its outbound proxy. That solves the problem.

Depends on what your use of 'outbound proxy' is. If only UAs can use
outbound proxies, proxy-removes-Route works. In the acme.com example I
raised, the 'interior' host (sales.acme.com) also uses an outbound
proxy, the acme.com proxy. For firewall traversal, this may well be
needed. Maybe the general rule of "if you're using an outbound proxy,
don't touch the Route header" might work. Presumably, each host knows
whether it is using an outbound proxy. May still cause some difficulty
if the Route header points to the outbound proxy.

However, in any case, the UA would have to use the regular destination
URL (typically, To) in the R-URI.

Definitely needs to be discussed in the text.

-- 
Henning Schulzrinne   http://www.cs.columbia.edu/~hgs