Identifying and requesting data in network using identifiers which are based on contents of data

摘要

In a system in which a set of data items are distributed across a network of servers, at least some of the data items being cached versions of data items from a source server, a content delivery method includes determining a data identifier for a particular data item, the data identifier being determined using a given function of the data comprising the particular data item; and responsive to a request for the particular data item, the request including at least the data identifier of the particular data item, providing the particular data item from a given one of the servers of the network of servers. The request for the particular data item may be resolved based on a measure of availability of at least one of the servers, where the measure of availability may be a measurement of bandwidth to the server; a measurement of a cost of a connection to the server, and/or a measurement of a reliability of a connection to the server. The function used to determine the identifier may be a message digest function or a hash function.