Some ISP networks might intercept all attempts you make to connect to the web (by means of the HTTP protocol on TCP port 80), and route your request through a transparent web proxy cache, technically known as an interception proxy. Your ISP does this in order to reduce the traffic on their backbone, and to reduce the traffic they have to pay for on other operators' networks.

If a proxy cache works well, it can also improve performance for the customer, by supplying locally cached copies of web pages and graphics much more quickly than by fetching them from the remote original web server.

However, when the proxy web cache is overloaded, it can make your web browsing appear slower than the nominal speed of your cable modem. For this reason, you should not rely on HTTP download speeds as evidence of the practical speed of your cable modem.

If a customer is having slow speeds in surfing but all the troubleshooting including pinging and trace route tests do not indicate a problem have them go to this link http://www.all-nettools.com/pr.htm to see if they are surfing thru a Web Proxy". If so go here to learn about a web proxy!

Refreshing stale pages in the web cache
While a copy of a page is stored in a proxy cache, the original page could be updated, and users would never see it, because the proxy will return the stale copy to users. Even if an MSIE user clicks on Refresh, the proxy will still return the stale version.

The fix for MSIE for Windows is Ctrl-Refresh (hold down the Ctrl key while clicking on Refresh) or Ctrl-F5, which causes the transparent proxy to refresh its copy of the page from the original web server. However, this appears not to work with:

MSIE v5.5 unless it has been updated with Service Pack 1 or higher (use Windows Update). MSIE v5.5 (without the service pack) was the version of MSIE supplied with Windows 2000 and Windows ME. MSIE 5.01 and MSIE 5.01 SP1.

How to sidestep the transparent web caches
When the transparent proxy cache breaks down, you lose all contact with the web. Because it is a transparent cache, there is no setting you can adjust on your computer to cause it to go direct to the remote site rather than via the proxy.

You can however defeat the transparent web cache by configuring your web browser explicitly to use another proxy cache that accepts requests on a port other than 80 (typically 3128 or 8080). Because the request is made on a port other than 80, the transparent cache does not intervene. But please note that
the performance from a proxy cache outside your ISP's network is bound to be poorer than performance from a properly working cache on your network, so you might wish to revert to normal working when your ISP's system has recovered.

The following procedure works on all Windows platforms running Internet Explorer 5.x/6.x, and the procedure for Internet Explorer 4.x is very similar:

Open Control Panel.
Double-click Internet Options.
Click on the tab Connections.
Click on button LAN Settings.
UNcheck Automatically detect settings.
UNcheck Use automatic configuration script.
Check Use a proxy server but ensure that the boxes are left blank.
Click on button Advanced.
In the row HTTP fill in (for instance) webcache.bt.net and port 8080. It is essential
that you do not select port 80, even if your chosen server offers a proxy service on
that port.

Ensure that the other rows are left blank.
UNcheck Use the same proxy server for all protocols.
In the Exceptions box enter: 192.168.*
Click OK.
Click OK to exit LAN settings.
Click OK to apply the changes and exit Internet Options.