Most WWW clients use memory and disk caches for speeding up accesses to frequently used web documents. In collaborative caching schemes, read access to cached document is given to the cooperating group of users. Such an integration creates an illusion of a single cache of much bigger size. Since all users of the group use the same integrated cache, it has an added advantage that the probability of the next accessed document being found in the cache is high. Collaborative caching schemes provide a better hit ratio than individual caching schemes.
Proxy servers control all accesses to the web from the subnet they service.
Caching Proxies can be designed in a centralized or distributed fashion. In the centralized design, in addition to servicing the requests of the clients from the subnet, a proxy also caches the documents in its local cache. Here, the cache maintained by the proxy contains the documents accessed by all the individual clients. Systems that use centralized servers are not considered fault tolerant and can become hot-spots and bottlenecks when the load is high. The issues become more prominant when a single proxy is the only gateway to the internet for a large group of users.