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The Internet Cache Protocol (ICP) is a UDP-based protocol used for coordinating web caches. Its purpose is to find out the most appropriate location to retrieve a requested object from in the situation where multiple caches are in use at a single site. The goal is to use the caches as efficiently as possible, and to minimize the number of remote requests to the originating server. ==Operation== Hierarchically, a queried cache can either be a parent or a sibling. Parents usually sit closer to the internet connection than the child. If a child cache cannot find an object, the query usually will be sent to the parent cache, which will fetch, cache, and pass on the request. Siblings are caches of equal hierarchical status, whose purpose is to distribute the load amongst the siblings. When a request comes into one cache in a cluster of siblings, ICP is used to query the siblings for the object being requested. If the sibling has the object, it will usually be transferred from there, instead of being queried from the original server. This is often called a "near miss" — the object was not found in the cache (a “miss”) but it was loaded from a nearby cache, instead of from a remote server. The ICP protocol was designed to be lightweight in order to minimize round-trip time between caches. It is intended for unreliable but quick connections. This approach can reduce numbers of server retrievals, and also prevent the storage of multiple copies of an instance of data, but leads to the potential drawback of increased intercache communication, which can slow the system down.〔 publisher|IEEE 〕 The ICP protocol is described in RFC 2186, its application to hierarchical web caching in RFC 2187. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Internet Cache Protocol」の詳細全文を読む スポンサード リンク
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