SafetyNet: A language-based approach to programmable networks

It appears that some degree of programmability is inevitable within the net work, whether it be through active networks, active services, or programmab le middleware. We argue that programming network elements with languages de signed for use within a single machine is inappropriate, since the only def ense for the shared resource of the network is through the use of sandboxes ? which are prone to performance problems and are difficult to implement co rrectly. Instead, we believe that new languages should be designed for prog rammable networks, using type systems that ensure safe programs, and encour age correct programs. We have designed and provided the full semantics for such a language, SafetyNet. Building upon this, we have implemented a compi ler, run time environment and a simulation environment for our language. In this paper we describe the major features of the language that protect the network: abstracted locations; located objects; volatile routing; thread a nd class loading; and enforced resource counting. We show how these feature s are used in a number of small case studies, and in implementing optimised communication libraries. We describe the implications of the language desi gn for the implementation of the run time support environment. The ease wit h which these demonstrations have been built and debugged shows the potenti al for enforcing network programming models with well-typed languages. (C) 2001 Elsevier Science B,V, All rights reserved.