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RE: Proxy-Connection header definition?

From: Marc Slemko <marcs@znep.com>
Date: Tue, 26 Jan 1999 12:38:31 -0800 (PST)
To: Yaron Goland <yarong@microsoft.com>
Cc: http-wg@cuckoo.hpl.hp.com
Message-Id: <Pine.BSF.4.05.9901261224160.11644-100000@alive.znep.com>
X-Mailing-List: <http-wg@cuckoo.hpl.hp.com> archive/latest/327
On Tue, 26 Jan 1999, Yaron Goland wrote:

> I too am unaware of a formal definition but we implement it in IE 4.0 and IE
> 5.0. I also believe we implement it in IE 3.0 but am too lazy to go back and
> check. It has worked out quite well for us allowing us to authenticate


> against HTTP/1.0 proxies without worrying about breaking against 1.0 proxies
> that don't support the mechanism and thus always pass the header on.

No.  The whole problem is that it doesn't work with proxies that don't
understand it if you have anything more complex than client to
proxy to origin server.

 From what I know, Netscape wanted a quick hack to let them do
persistent connections to proxy servers without having to have all
clients and proxies and servers support it.  Unfortunately, their
quick hack was too hacky and quickly falls apart when you have chains
of proxies.

C(a) -> P(b) -> P(c) -> O(d)

C is client, P is proxy, O is origin server.

a sends a Proxy-Connection to b.  b doesn't understand the Proxy-Connection
header, so it passes it on.  c understands it, so it tries to do a 
persistent connection with b.  Things break.

What the Proxy-Connection header has done is require that every
proxy which can pass requests to an "upstream" proxy of some type
know about it or be "broken".  In reality, it is the concept of the
Proxy-Connection header that is broken, but given that clients implement
it and other proxies implement it, the only thing this poor little 
standards conforming proxy can do is deal with it as well. 

It doesn't, of course, have to do anything other than drop it from 
forwarded requests, but that still involves dealing with it.

In fact, you even run into this problem sometimes in situations
where the proxy thinks it is talking directly to the origin server,
due to hacks like broken "transparent proxies" (which, of course, by
definition are broken), broken "reverse proxies" that think they are
still proxies (eg. www.novell.com used to be behind one), etc.
These cases are different though, since it is much more arguable
that the "normal" proxy isn't the thing that should be fixed.
Received on Tuesday, 26 January 1999 12:40:27 UTC

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