When an origin web server sends a response, the client's browser stores the response in its local cache. If the object has no expiration time, the browser makes subsequent requests for that content using a conditional GET request in the form of an extra request header field, such as If-Modified-Since. If the requested object is different than the content that the browser has cached, the origin web server sends a fresh copy of the object to the browser. Otherwise, the browser uses the object that is cached locally.
Although it is faster than serving the entire object each time the browser requests it, conditional GET requests can add up to a significant amount of traffic for your site. For example, if your site has several images for each page, clients might perceive a slow response time because of the large number of conditional GET requests for the image objects.
Perform these tasks to reduce or eliminate requests to your site for relatively static content by enabling the web browser's cache to serve qualifying content.
The following prerequisites apply to enable Intelligent Browser Referencing (IBR).