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International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / The current challenge has been to develop and adapt commercial Internet protocols for usage in space communications. Commercialized solutions, rather than Customized ones are cheaper, have low turnaround time and offer higher flexibility in deployment and operation. The focus of the study was to modify and develop UDP/IP based protocols commonly used in commercial Internet for reliable data transfers in space environment. Multicast Dissemination Protocol was designed by Naval Research Laboratory to provide reliable multicast data and file transfer delivery on the top of general UDP/IP platform. It is very suited for bulk data transfer over the Internet. We have extended its usage in space channels and evaluated it as a solution to meet key challenges in space communications like high bit error rates and asymmetric channels. We have also tried to optimize the performance of the protocol in the terms of throughput, reliability, integrity and security of data. The evaluation test were carried on our Space to Ground Link Simulator which uses PPP to model point to point satellite links and correspond to low capacity systems as found in small satellite systems.

Testing is the dominant technique for quality assurance of software systems. It typically consumes considerable resources in development projects, and is often performed in an ad hoc manner. This thesis is concerned with model-based testing, which is an approach to make testing more systematic and more automated. The general idea in model-based testing is to start from a formal model, which captures the intended behavior of the software system to be tested. On the basis of this model, test cases can be generated in a systematic way. Since the model is formal, the generation of test suites can be automated and with adequate tool support one can automatically quantify to which degree they exercise the tested software. Despite the significant improvements on model-based testing in the last 20 years, acceptance by industry has so far been limited. A number of commercially available tools exist, but still most testing in industry relies on manually constructed test cases. This thesis address this problem by presenting a methodology and associated tool support, which is intended to be used for model-based testing of communication protocol implementations in industry. A major goal was to make the developed tool suitable for industrial usage, implying that we had to consider several problems that typically are not addressed by the literature on model-based testing. The thesis presents several technical contributions to the area of model-based testing, including - a new specification language based on the functional programming language Erlang, - a novel technique for specifying coverage criteria for test suite generation, and - a technique for automatically generating test suites. Based on these developments, we have implemented a complete tool chain that generates and executes complete test suites, given a model in our specification language. The thesis also presents a substantial industrial case study, where our technical contributions and the implemented tool chain are evaluated. Findings from the case study include that test suites generated using (model) coverage criteria have at least as good fault-detection capability as equally large random test suites, and that model-based testing could discover faults in previously well-tested software where previous testing had employed a relaxed validation of requirements.

Modern computer systems are advancing from multi-core to many-core designs and System-on-chips (SoC) are becoming increasingly complex while integrating a great variety of components, thus constituting complex distributed systems. Such architectures rely on extremely complex communication protocols to exchange data with required performance. Arguing formally about the correctness of communication is an acknowledged verification challenge. This thesis presents a generic framework that formalises the idea of incremental modelling and step-wise verification to tackle this challenge: to control the overall complexity, features are added incrementally to a simple initial model and the complexity of each feature is encapsulated into an independent modelling step. Two main strategies reduce the verification effort. First, models are constructed with verification support in mind and the verification process is spread over the modelling process. Second, generic correctness results for framework components allow the verification to be reduced to discharging local assumptions when a component is instantiated. Models in the framework are based on abstract state machines formalised in higher order logic using the Isabelle theorem prover. Two case studies show the utility and breadth of the approach: the ARM AMBA Advanced High-performance Bus protocol, an arbiter-based master-slave bus protocol, represents the family of SoC protocols; the PCI Express protocol, an off-chip point-to-point protocol, illustrates the application of the framework to sophisticated, performance-related features of current and future on-chip protocols. The presented methodology provides an alternative to the traditional monolithic and post-hoc verification approach.

Flecs is a framework for facilitating rapid implementation of communication protocols. Forwarding functionality of protocols can be modeled as a combination of packet processing components called abstract switching elements or Ases. The design of Ases is constrained by the axioms of communication which enables us to formally analyze forwarding mechanisms in communication networks. Ases can be connected in a directed graph to define complex forwarding functionality. We have developed Flecs on top of the Click modular router. The compilers in the Flecs framework translate protocol specifications into its Click implementation. We claim that the use of our framework reduces the implementation time by allowing the programmer to specify Ases and the forwarding configuration in a high-level meta-language and produces reasonably efficient implementations. It allows rapid prototyping through configuration, as well as specialized implementation of performance-critical functionality through inheritance.

FlexRay, developed by a consortium of over hundred automotive companies, is a real-time in-vehicle communication protocol for automotive networks. It is being used as a higher-performance, time-triggered, and deterministic serial bus in automobiles for many safety-critical and x-by-wire systems. In x-by-wire systems the hydraulic parts of systems such as steering and braking are replaced with electronics. As x-by-wire systems are safety-critical, they must be fault-tolerant, deterministic, and should have synchronized time base (global time). FlexRay fulfils all these requirements as it is a deterministic and fault-tolerant serial bus system with data rates of 10 Mbps for extremely safety- and time-critical applications. As, FlexRay has become the de-facto standard for high speed safety-critical communications in automotive domain, and timing analysis of FlexRay still continues to generate significant research interest. The FlexRay allows both time-triggered and event-triggered messages. The static (ST) segment allows time-triggered transmission, while dynamic (DYN) segment allows event-triggered transmission. As the DYN segment transmits messages based on their priorities; so the delay suffered by a message depends on the interferences by its higher priority messages. Computing interferences of the higher priority messages is a challenging problem for the DYN segment of FlexRay [32]. So, in order to compute interferences of the higher priority messages one way is to use simulation technique. The SystemC simulator proposed in this thesis is used to model and simulate the behaviour of the DYN segment of the FlexRay protocol. This modelling and simulation is done on system level using the system description language SystemC. The simulator estimates the delay suffered by a message instances because of the interferences of higher priority messages. This estimation of delay is done by taking no-jitter/jitter into consideration. Finally, in both the cases the delay suffered by each and every message instance is plotted.

Flecs is a framework for facilitating rapid implementation of communication protocols. Forwarding functionality of protocols can be modeled as a combination of packet processing components called abstract switching elements or Ases. The design of Ases is constrained by the axioms of communication which enables us to formally analyze forwarding mechanisms in communication networks. Ases can be connected in a directed graph to define complex forwarding functionality. We have developed Flecs on top of the Click modular router. The compilers in the Flecs framework translate protocol specifications into its Click implementation. We claim that the use of our framework reduces the implementation time by allowing the programmer to specify Ases and the forwarding configuration in a high-level meta-language and produces reasonably efficient implementations. It allows rapid prototyping through configuration, as well as specialized implementation of performance-critical functionality through inheritance.