Adapting Distributed Applications Using Extensible Networks
Résumé
In this paper, we show that the adaptation of distributed software components can be performed by extending network behavior with Application-Specific Protocols (ASPs). We propose to program ASPs in PLAN-P, a domain specific language designed for active networks. We illustrate the application scope of ASPs with three examples: (i) audio broadcasting with bandwidth adaptation in routers, (ii) an extensible HTTP server with load-balancing facilities, (iii) a multipoint MPEG server derived from a point-to-point server. To reconcile portability and efficiency, the PLAN-P run-time system includes a JIT compiler which is generated automatically from a portable interpreter. Measurements show no performance degradation due to PLAN-P; an ASP can be as efficient as a built-in C version of the same program. Finally, we show that our implementation framework for PLAN-P can be easily evolved, since it is based on an interpreter.