W3C home > Mailing lists > Public > ietf-http-wg-old@w3.org > January to April 1997

Re: Ignore proxy

From: Josh <josh@netscape.com>
Date: Wed, 2 Apr 1997 03:58:30 -0800 (PST)
To: Adam Wierzbicki <adamw@icm.edu.pl>
Cc: http-wg@cuckoo.hpl.hp.com, adamw@icm.edu.pl, mkur@icm.edu.pl, jwr@icm.edu.pl, wojsyl@icm.edu.pl
Message-Id: <ML-3.1.859982310.6838.josh@pulse>
X-Mailing-List: <http-wg@cuckoo.hpl.hp.com> archive/latest/2974
> Please ignore this message if it is a FAQ.
> I wanted to know if there is a way for a proxy to tell a client
> any/all of the following things:
> 1. Ignore me and fetch this document yourself. (but if you call me
> again I might change my mind.)
Not presently, there is a 305 and maybe 306 redirect which may
allow this functionality to be discussed at memphis.
Current implementations do not allow this.
A workaround is using a Proxy Auto Config file, where
you specify a failover, that way if the proxy is unavailable,
the client will go direct. ( assuming the network allows it )

> 1a. Ignore me for some time.
same as above
> 2. I will not fetch this for you.  (the "Not Authorized"  response?)
Yes, the 407  Proxy Authentication Required response is used.

> 2a. I will not cache this for you.
> I see this as a way (analagous to "Come Back Later") for a very busy
> proxy to tell clients that they are on their own.  Also, a caching
> proxy might want to tell a user agent that it will not cache its
> requests.  Of course, there are problems with proxies which are
> gateways -- they should never refuse proxying, but still might refuse
> caching.

For a busy server, it generally makes sense for it to cache
if it has to retreive it anyway.  Of course, we're assuming
the object isnt already in the cache-- if it is, then the
proxy can potentially return it from the cache.

The biggest cost for a proxy is the origin retreive (contacting 
the web server ), writing a cache file is much cheaper.
In addition, by caching it, if there is a request for the
same object, the proxy can then return it from the cache 
next time, which helps the proxy a great deal.

I think in a worst case scenario, it would be O.K. for the
proxy to act such that:
"I am too busy to go to the far away web server for you, but
Ill give you what I have in my cache, even though its out of date".
The client can accept that or attempt to go direct.

> Thank you in advance.  

Josh Cohen				        Netscape Communications Corp.
Netscape Fire Department	     	       "Mighty Morphin' Proxy
Server Engineering
josh@netscape.com                       http://home.netscape.com/people/josh/
Received on Wednesday, 2 April 1997 03:58:27 UTC

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