iTP Secure WebServer System Administrator's Guide (iTPWebSvr 5.1+)

Administering Session Identifiers for Anonymous
Sessions
iTP Secure WebServer System Administrator’s Guide—522659-001
11- 9
Advanced Configuration Options
As shown in Figure 11-3, proxies act as intermediaries between a group of web clients
and web servers.
When a web client issues a request in the form of a URL, the proxy first checks its cache
to see if it already has the resource. If so, the proxy returns the resource to the web
client, sometimes without contacting the web server at all. If the proxy doesn’t have the
requested resource, it forwards the request to the specified web server.
The use of proxies prevents an accurate measure of the number of times a web page is
accessed because there is no way to know how often a proxy short-circuits a request by
returning a page from its own cache. Using tickets can reduce the problem considerably
because each request can have a unique ticket embedded in it. So even though many
users may request the same web page, the presence of a unique ticket will make it
appear to the proxy as though each request is unique. For example, user X’s request
might be
http://www.acme.com/@@4RTgh67j8S23c5d3/info.html
whereas user Y’s request is
http://www.acme.com/@@H9bF3f0Df36Gpp3Cd/info.html
The proxy, therefore, will successfully find a page in its cache only if the same user
requests the same page a second time. Note, however, that this method works only if the
ticket is embedded in the URL. By default, the content server does not insert tickets in
URLs if cookies are enabled and the web client supports cookies.
Figure 11-3. Proxies
111CDT .CDD
Web Client Web Client Web Client Web Client Web Client
Web Server Web Server Web Server
Proxy
Server
Cached
Requests
and Replies