A language-based approach to protocol implementation.

Abstract

This thesis explores two strategies for supporting the development of network communication software: imposing constraints on protocol design at the specification level, and using a special-purpose language for protocol implementation. It presents a protocol implementation language called Morpheus. Morpheus utilizes the new strategies to provide a higher level of abstraction, finer grain modularity, and greater software reusability than previous approaches. Morpheus is able to provide a high level of abstraction because of built-in knowledge about its problem domain. It has a narrow problem domain--network protocols--that is further narrowed by the application of specification-level constraints. One particular constraint--the shapes constraint, which partitions protocols into three basic kinds--is particularly effective in raising the level of abstraction. Morpheus's support for modularity and, indirectly, software reuse hinges on reducing the performance penalty for layering. When protocol layering entails a high performance cost, developers are motivated to build complex monolithic implementations that are hard to design, implement, debug, modify, and maintain. Morpheus reduces the performance costs of layering by applying optimizations based on common patterns of protocol execution. If the degree of modularity is held fixed, then the optimizations simply improve performance. An optimization based on Integrated Layer Processing is particularly noteworthy for its dramatic contribution to network throughput while preserving modularity.