Study of piggyback cache validation for proxy caches in the World Wide Web

1 Introduction A proxy cache acts as an intermediary between potentially hundreds of clients and remote web servers by funneling requests from clients to various servers. In the process, the proxy caches frequently requested resources to avoid contacting the server repeatedly for the same resource if it knows, or heuristically decides, that the information on the page has not changed on the server. A problem with caching resources at a proxy or within a browser cache, is the issue of cache coherency--how does the proxy know that the cached resource is still current [6]? If the server knows how long a resource is valid (e.g., a newspaper generated at 5:00am daily), the server can provide a precise expiration time. Cached copies are always fresh until the expiration time. More commonly, the resource that is made available has no clear expiration time. It may change in five minutes or remain unchanged for a long time