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6.9.1 Cache access protocols


The cache supports three access protocols: tcp, (called encapsulating in [7]), udp (called connectionless in [7]), and ascii (called proxy-http in [7]). The tcp protocol encapsulates cache-to-cache data exchanges to permit end-to-end error detection via checksums and, eventually, digital signatures. This protocol exchanges an object's remaining Time-To-Live (TTL). The cache uses the udp 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 tcp and udp protocols both support end-to-end reliability, the ascii protocol is the supported by most Web browsers (e.g., NCSA Mosaic, Netscape, and Lynx), in so-called proxy mode. 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. Proxy access is transparent to the user.


In Harvest v1.3, we added an unsupported, user-contributed patch to the Cache which allows WAIS proxy access. To enable this functionality, set the wais_relay variable in your cached.conf to the host and port on which your WAIS server is running.

Duane Wessels
Wed Jan 31 23:46:21 PST 1996