Command Execution in a Heterogeneous Environment*

As a user's computing environment grows from a single time-shared host to a network of specialized and general-pwpose machines, the capability for the user to access all of these resources in a consistent and transparent manner becomes desirable. Instead of viewing commands as binary files, we expect the user to view commands as services provided by servers in the network. The user interacts with a personal workstation that locates and executes services on his behaH. Executing a single service provided by any server in the network is useful, but the user would also like to combine services from different machines to perform complex computations. To provide this facility we expand on the UNIX notion of pipes to a generalized pipeline mechanism containing services from a variety of servers. In this paper we explain the merits of a multi-machine pipeline for solving problems of accessing services in a he~erogeneous environment. We also give a design and performance evalua~ion of a general mechanism for mul~i-machine pipes using ~he DARPA UDP and TCP protocols. ·This work was supported in pa.rt by gra.nts from the Na.tional Science Foundation (MCS-8219178), SUN Microsystems Incorporated, and Digital Equipment Corporation.