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Re: Changes to svn_ra.h for proxy support

From: Daniel Stenberg <daniel_at_haxx.se>
Date: 2001-09-28 10:55:10 CEST

On 27 Sep 2001, Ben Collins-Sussman wrote:

> Greg, can you comment on this? The truth is, I don't really understand
> how proxies work in general. And I certainly don't understand how they
> work in terms of neon<->apache traffic. Maybe someone can explain?

In general, HTTP proxies work like this:

Instead of connecting to a remote server, you connect to the local proxy and
ask for the remote document. The difference to the local client is very
minor, there's only a slight difference in how the request looks.

HTTP proxies may require authentication (and that works exactly the same way
a remote site may require it, only using a different header). One vendor
introduced their own authentication protocol named NTLM that is proprietary
and only supported by IE why numerous browser users are fenced in when using
a proxy from that vendor. There are reverse-engineered implementations of
NTLM-code but neon does not support that as of now.

Many companies run proxies for "external" machines and allow "internal"
machines get accessed directly. That's why some loonie invented the
"automatic proxy configuration" files (.pac in netscape/mozilla), which is a
piece of javascript that when fed with a URL returns which proxy to use.
Thus, some places even use different proxies for different remote hosts
etc...

HTTPS through a HTTP proxy is done differently. Then the client tells the
proxy to "tunnel-through" everything from the client to the specified remote
host, as encryption and everything needs to pass in and out unmodified. Since
this tunneling is done without any control or supervision from the proxy,
most companies block their proxies for HTTPS access to non-default ports
(443).

-- 
      Daniel Stenberg - http://daniel.haxx.se - +46-705-44 31 77
   ech`echo xiun|tr nu oc|sed 'sx\([sx]\)\([xoi]\)xo un\2\1 is xg'`ol
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Received on Sat Oct 21 14:36:42 2006

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