Cache Manager

Each proxy server has a cache manager which maintains a cache of documents available as a result of user requests, pre-fetches, and hoard-walks. When the proxy server receives a request, if the document is not available at the cache, the request is forwarded to the next level of proxy or directly to the WWW server. Note that the browser cache is disabled, since all user requests must go through to the local proxy server in order to build an accurate user profile.

Should disconnections arise, the local cache manager is also responsible for providing the documents. In our system, if any control connection with the backbone machine is broken prematurely, the local proxy server will go into a disconnected mode. In this mode, it will only present to the browser the items on the local cache. If a request is made for an item that was not hoarded, the local cache manager returns an empty file. The browser will then present a ``Document contains no data'' message to the user.

The backbone cache manager is any standard off-the-shelf proxy server. In the current implementation, we use Squid [4].