Performing remote operations efficiently on a local computer network

Abstract

This paper discusses communication among computers connected by a very high speed local network and focuses on ways to support distributed programs that require efficient interprocessor communication. It is motivated by the availability of increasingly high speed local networks and inefficiencies in existing communication subsystems. Mechanisms such as remote procedure calls, monitor calls, and message passing primitives are bases for interprocessor communication at high levels (i.e., within a programming language). At lower levels, interprocessor communication occurs via the transmission of data over some communication medium. On a local network, this basic communication mechanism is the transmission of packets. This paper is concerned with an intermediate communication layer for high speed local networks. To provide overall efficiency, this layer should provide communication primitives that (1) are a good basis on which to implement high level primitives and (2) are specialized enough to be implemented efficiently; for example, in a combination of microcode and hardware. To analyze communication primitives for this intermediate layer, we present a communication model called the remote reference/remote operation model in which a taxonomy of communication primitives is defined. We illustrate the model by describing an implementation of simple communication primitives on Xerox Alto computers interconnected with a 3 megabit Ethernet.