DeleGate: A General Purpose Application Level Gateway

Abs t rac t . DeleGate is a general purpose application level gateway which relays a variety of application protocols on the Interllet~ including HTTP, FTP, Gopher, WAIS, NNTP, SMTP, POP, Telllet, X Window and CUSeeMe. It overcomes a variety of obstacles on the Internet caused by barriers for security, insufficient band width and mismatching among protocol specifications and implementations. An application level gateway mediates communication between clients and servers recognizing the syntax and semantics of application protocols it is relaying. Therefore it can supply vm'ious functions like caching mid translation to an application protocol, for its procedure and data~ without changing clients and servers. This paper presents an overview of DeleGate and its two unique features termed mounting and connection cache. Mounting is a mechanism which provides a virtual view for a name space of networked resources by illtering, aliasing and merging names from original name spaces. Resource names transferred as data on each protocol are recognized and rewritten by DeleGate. Connection cache allows established connections to servers to be re.sources which are sharable and reusable among clients. It reduces the cost of repetitive connection establishments to the same server, where the repetition is introduced by an application protocol gateway which relays between different protocols.