Re: [squid-users] Refresh problems with IE6?

On Thursday 03 July 2003 17.24, misleb@onshore.com wrote:

> I really don't want to turn on IMS requests for EVERY object ALL
> the time. That would just be silly.

Then you should not be running a transparent proxy, but have the proxy
configured in the browsers.

> Seems like this would be a very common problem transparent caching.

Yes, because transparent proxying is broken by design. The fault is
with no doubt in the act of "transparently" intercept port 80 traffic
not intended for a proxy. While such interception is a clever trick,
it is not a good way to get browsers to use a proxy and is in
violation of the TCP/IP standard. (it violates the end-to-end
semantics of IP addressing, a fundamental assumption upon all other
Internet protocols is built).

> Does a transparent cache really know the difference between a
> browser refresh and a normal HTTP "GET" request?

No, and this because the browser does not know there is a proxy cache
and thus does not include cache control directives to tell the proxy
cache to fetch a fresh copy.

If you configure your browser to use a proxy then it knows there is a
proxy which might cache content and therefore includes suitable cache
control directives in the request when you push the reload button to
control proxy caches.

Some browsers (or versions of browsers) send these cache control
headers even when not configured to use a proxy, and only such
browser versions work well together with transparently interception
proxies.

Regards
Henrik

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