ntl request that caching is controlled responsibly, otherwise network traffic is increased and page delivery is slowed down.

• Use HTTP 1.0 Headers (server-side directives) - these will manage caching throughout the DTV architecture.
• Manage cache of html/js pages and images separately (maximise caching of images - image directories - as much as possible)
• Any https content and URLs containing query strings ("?"), "cgi" or "asp" will not be cached

Managing caching by the Proxies:

These are some HTTP 1.0 Headers you might consider using:

• Expires - gives the date/time after which the entity should be considered stale.
• If-Modified-Since - if the requested resource has not been modified since the time specified in this field, a copy of the resource will not be returned from the server
• Last-Modified - indicates the date and time at which the sender believes the resource was last modified
• Pragma: no cache - forwards the request toward the origin server even if it has a cached copy of what is being requested. Only use this in very specific instances.

See http://www.w3.org/Protocols/HTTP/1.0/spec for more specific details on how to implement.

Managing set-top box cache:

If you wish to ensure the HTML page is not cached on the STB, use the META tag. (NB: This will ONLY manage the cached content on the set-top box - NOT the proxy servers)

• The "expires" value sets a date and time for expiry
• The "pragma" value ensures the page is not cached on the set-top box at all
• The "refresh" value specifies a delay, in seconds, before the browser automatically reloads the document

NB: All Proxy caching is switched OFF in the ntl development environments.

Developers should also be aware that there may be caching functionality which exists on their OWN network and appropriate action will need to be taken.