A distributed UNIX system based on a virtual circuit switch

Abstract

The popular UNIXTM operating system provides time-sharing service on a single computer. This paper reports on the design and implementation of a distributed UNIX system. The new operating system consists of two components: the S-UNIX subsystem provides a complete UNIX process environment enhanced by access to remote files; the F-UNIX subsystem is specialized to offer remote file service. A system can be configured out of many computers which operate either under the S-UNIX or the F-UNIX operating subsystem. The file servers together present the view of a single global file system. A single-service view is presented to any user terminal connected to one of the S-UNIX subsystems. Computers communicate with each other through a high-bandwidth virtual circuit switch. Small front-end processors handle the data and control protocol for error and flow-controlled virtual circuits. Terminals may be connected directly to the computers or through the switch. Operational since early 1980, the system has served as a vehicle to explore virtual circuit switching as the basis for distributed system design. The performance of the communication software has been a focus of our work. Performance measurement results are presented for user process level and operating system driver level data transfer rates, message exchange times, and system capacity benchmarks. The architecture offers reliability and modularly growable configurations. The communication service offered can serve as the foundation for different distributed architectures.