How does P3P impact Web performance?
In a distributed system like the World Wide Web, with high network latencies and never enough bandwidth, caching is very important to give acceptable performance to users. In this light, it is important to consider the interaction of P3P with caches in the network. The P3P-Specification contains a whole subtree on the subject of caching policies and references. But already in the design of P3P, the group spent a lot of effort to improve performance. With the policy-reference file, a server can define for a whole site, which policy applies to which “realm” or page. The link to this file can be given by a Head-request or by a LINK-tag within the header of a HTML-page. The use of LINK-tag/Header in conjunction with a policy reference file reduces the amount of transfered data and spares additional roundtrips.
