Network operating system kernels for heterogeneous environments

Abstract

A major function of a Network Operating System Kernel is to free application program developers from the need for designing complex protocols. The Operating System analogy for networks offers a paradigm for inter-program cooperation, as if this cooperation were local. Instead of forcing programs to send and interpret messages explicitly, the Network Operating System provides services for remote operations on accustomed data structures, whereby the message exchange as such remains invisible to the programmer.

This paper compares two extremes in the range of Network Operating System Kernel interfaces currently under discussion: the “simple” Remote Procedure Call and the more “complex” Remote Service Call. The Remote Service Call is a straightforward generalization of the Remote Procedure Call interface and is designed to encompass the pertinent functions and services which are proven and available in local operating system kernels. By analysis, it will be shown that the “simple” approach, although desirable, does not fulfil all basic functional requirements. Among these are aspects of pluralism, such as protection and scheduling, other system aspects, such as revocability and concurrency e.g. as needed by file servers, aspects of heterogeneity, such as the issue of data presentation, and the support of higher level objects, such as open files. The price to be paid for the complexity in terms of implementation effort, reliability, and portability will be discussed on the basis of a prototype implementation of a Remote Service Call facility in a network of heterogeneous computing systems.