Proxy Issues Forward Proxy Caching Proxies Reverse Proxy

Proxy Issues

Proxying is a common technique of managing network connections for a variety of purposes. Many schools which access the ELabs site will do so through a proxy server. Some proxy servers try to be efficient and cache results, which can cause problems with an analysis. Many schools need to have web filtering in place to satisfy legal requirements, and it's natural for them to combine this with a proxy server.

We can also make use of a "reverse" proxy to make services running on several different machines appear to come from one web site.

Forward Proxy

Here is a common use scenario: a school district sets up a proxy server for all schools in the district. Anytime a browser makes a request for a web page, it goes to the proxy server, and the proxy server relays the request to the website. The proxy server gets the web page or other file requested, and then serves it back to the browser that requested it.

There are a number of reasons for doing this:

• The proxy server can keep a record of all traffic between the browser and the web
• The proxy server can filter the content, preventing students from accessing "bad" websites
• The proxy server can cache pages (save a copy) for efficiency. If several browsers ask for the same web page, they can receive a copy from the proxy server, rather than generating multiple redundant requests for the same web page.

While caching proxies can improve page loading speed, they also present problems when dealing with dynamically generated content, as in an analysis performed as part of an ELabs e-Lab.

Caching Proxies

(Notes here on how to deal with caching proxies, and to prevent caching of images).

Reverse Proxy

-- Main.EricMyers - 21 Jan 2008