Active networks present significant safety, security, and efficiency challenges. Domain-specific languages, i.e., languages providing only constructs relevant to a particular domain, provide a solution that balances these constraints. Safety and security can be ensured using verification techniques that exploit the restricted nature of such languages. Strategies have been developed for the compilation of domain-specific languages that provide both portability and efficiency. This paper presents a synthesis of work on the PLAN-P domain-specific language for programmable routers. We present the language design, representative experiments that have been carried out using the language, and new compilation strategies. End-to-end performance is typically comparable to that of hand-coded C implementations.

Active networks have been proposed to allow the dynamic extension of network behavior by downloading application-specific protocols (ASPs) into network routers. We demonstrate the feasibility of the use of ASPs in an active network for the adaptation of distributed software components. We have implemented three examples which show that ASPs can be used to easily extend distributed applications, and furthermore, that such adaptation can be safe, portable and efficient. Safety and efficiency is obtained by implementing the ASPs in PLAN-P, a domain-specific language and run-time system for active networking. The presented examples illustrate three different applications: audio broadcasting with bandwidth adaptation in routers; an extensible HTTP server with load-balancing facilities; and a multipoint MPEG server derived from a point-to-point server.

Domain-specific languages (DSL) have many potential advantages in terms of software engineering, ranging from increased productivity to the application of formal methods. Although they have been used in practice for decades, there has been little study of methodology or implementation tools for the DSL approach. We present our DSL approach and its application to a realistic domain: the generation of video display device drivers. The article focuses on the validation of our proposed framework for domain-specific languages, from design to implementation. The framework leads to a flexible design and structure, and provides automatic generation of efficient implementations of DSL programs. Additionally, we describe an example of a complete DSL for video display adaptors and the benefits of the DSL approach for this application. This demonstrates some of the generally claimed benefits of using DSLs: increased productivity, higher-level abstraction, and easier verification. This DSL has been fully implemented with our approach and is available. Compose project URL: http://www.irisa.fr/compose/gal.

Active networks are aimed at incorporating programmability into the network to achieve extensibility. One approach to obtaining extensibility is to download router programs into network nodes. This programmability is critical to allow multipoint distributed systems to adapt to network conditions and individual clients' needs. Although promising, this approach raises critical issues such as safety to achieve reliability despite the complexity of a distributed system, security to protect shared resources, and efficiency to maximize usage of bandwidth. This paper proposes the use of a domain-specific language, PLAN-P, to address all of the above issues. To address safety and security, we give examples of properties of PLAN-P programs that can be automatically checked due to the use of a restricted language. For efficiency, we show that an automatically generated run-time compiler for PLAN-P produces code which outperforms an equivalent compiled Java program. Additionally, we present performance results on a real application (learning bridge) where we obtain 100% of the maximum possible throughput.

Flexibility is recognized as a key feature in structuring software, and many architectures have been designed to that effect. However, they often come with performance and code size overhead, resulting in a flexibility vs. efficiency dilemma. The source of inefficiency in software architectures can be identified in the data and control integration of components, because flexibility is present not only at the design level but also in the implementation. We propose the use of program specialization in software engineering as a systematic way to improve performance and in some cases, to reduce program size. In particular, we advocate the use of partial evaluation, which is an automatic technique to produce efficient, specialized instances of generic programs. We study several representative, flexible mechanisms found in software architectures: selective broadcast, pattern matching, interpreters, layers, and generic libraries. We show how partial evaluation can systematically be applied in order to optimize those mechanisms.

The PRAM model has been shown to be an optimal design for emulating both loose and tightly coupled multiprocessors for unit time operations. When virtual processors are required, multiplexing work to available processors is employed. This introduces a form of latency incurred by operating system overhead. Further complications arise when bandwidth creates bottlenecking of work units. G.E. Blelloch (1989) showed how to add parallel prefix operations (scans) to an extended PRAM model which uses unit step, not time operations. This paper shows how the Psi( psi ) calculus can be used to group work units, i.e. pipelining the work units, so that multiplexing is not required. The authors instead pipeline work units to processors and show how the number of processors need not be equivalent to the number of data components. Partitioning array data structures and pipelining groups of partitions to processors can minimize latency and bottlenecking on distributed message passing multiprocessing architectures.>