Alfs : a file server for a heterogeneous environment

Abstract

This thesis investigates the design and implementation of a file server, Alfs, for a heterogeneous environment. Alfs can store files in a canonical form which allows them to be created on one system, stored on the file server, and retrieved by a second, different system. The file server handles all translations between system dependent data and file representations and the canonical storage used on the file server. To make the canonical form more compact and to allow record access, files in canonical form are described by a generic description. A generic description describes a file as a series of repeated records. The canonical form used by Alfs is based on ISO's ASN.l. Alfs has two other formats for storing files—text form and host context. Text form is a canonical form for text files, files that only contain printable characters. Host context is used to store files that are not convertible to a different context. This includes files such as program binaries. Alfs consists of two parts: a client and a server. The client resides on a user's machine and the server is on the server machine. The client and server communicate using ISODE which is an implementation of the top four levels of the ISO protocols.