The cache supports three access protocols: encapsulating, connectionless, and proxy-http. The encapsulating protocol encapsulates cache-to-cache data exchanges to permit end-to-end error detection via checksums and, eventually, digital signatures. This protocol also enables a parent cache to transmit an object's remaining time-to-live to the child cache. The cache uses the UDP-based connectionless protocol to implement the parent-child resolution protocol. This protocol also permits caches to exchange small objects without establishing a TCP connection, for efficiency. While the encapsulating and connectionless protocols both support end-to-end reliability, the proxy-http protocol is the protocol supported by most Web browsers. In that arrangement, clients request objects via one of the standard information access protocols (FTP, Gopher, or HTTP) from a cache process. The term ``proxy'' arose because the mechanism was primarily designed to allow clients to interact with the WWW from behind a firewall gateway.