A domain structure for distributed computer systems

Abstract

The successful implementation of generalized multiple computer systems will require attention both to the form of physical architecture and to the choice and implementation of a suitable systems environment in which to construct and run applications. This paper argues for the use of a multi-computer physical architecture in preference to a multi-processor architecture, and for dynamic distribution of functions and control as opposed to static allocation of functions and hierarchical control. A systems environment which is based on a domain structure is then described. The domain structure restricts sharing of items. This alleviates the main problem in implementing a capability mechanism to support domains in a system without shared memory, which is that a central table of capabilities is required. It also makes the management of the non shared items easier since they can be required only at one computer at a time. Essential sharing is also handled without central control but at the cost of some complexity. Considerable attention is paid to the handling of interdomain jumps as they provide the opportunity for the dynamic allocation of functions. It is conjectured that the resulting system would be capable of smooth expansion in size from one to twenty five computers. In operation it would exhibit dynamic load balancing as well as having the protection advantages of domain structure.