Using FTT-CAN to the Flexible Control of Bus Redundancy and Bandwidth Usage

DETIController Area Network (CAN) is a popular and very well-known bus system, both in academia and in industry, initially targeted to automotive applications as a single digital bus to replace the wiring that were growing complexity, weight and cost with the advent of new automotive appliances. However, requirements have evolved and CAN’s dependability and bandwidth limitations led to the emergence of alternative networks such as FlexRay and TTP/C. Nevertheless, we believe that it is possible to improve CAN so it could fulfill contemporary requirements. This paper proposes the use of Flexible Time-Triggered CAN (FTT-CAN) to increase the available bandwidth while providing fault tolerance in CAN based systems with multiple buses. The architecture and flexibility of FTT based systems enables a tight yet flexible control of redundancy and bandwidth usage without increasing the complexity of the nodes. In this novel solution, a FTT-CAN Master controls the dispatching of messages among a set of independent buses. The Master can react online to bus failures switching the transmission of critical messages to a non-faulty bus, always keeping a predetermined redundancy level

Position paper on time and event-triggered communication services in the context of e-manufacturing

Modern factories are complex systems where advances in networking and information technologies are opening new ways towards higher efficiency. Such move is being driven by market rules with ever-increasing competition levels, in search for faster time-to-market, improved process yield, non-stop operations, flexible manufacturing and tighter supply-chain coupling. All these aims present a common requirement, i.e. a realtime flow of information, from the plant-floor up to the management, maintenance, suppliers and clients, to support accurate monitoring and control of the factory. This stresses the importance achieved by the communication infrastructure in modern manufacturing industry. This paper presents the authors view concerning the current trends in modern factory communication systems. It addresses the problems of seamlessly integrating different information flows with diverse requirements, mainly in terms of timeliness. In this aspect, the debate between event-triggered and time-triggered communication is revisited as well as the joint support for both types of traffic. Finally, a view of where factory communication systems are moving to is also presented, showing the impact of open and widely available technologies.FCT. Comissão Europeia(ARTIST,IST-2001-34820

Scheduling with Optimized Communication for Time-Triggered Embedded Systems

We present an approach to process scheduling for synthesis of safety-critical distributed embedded systems. Our system model captures both the flow of data and that of control. The communication model is based on a timetriggered protocol. We take into consideration overheads due to communication and the execution environment. Communications have been optimized through packaging of messages into slots with a properly selected order and lengths. Several experiments demonstrate the efficiency of the approach. 1

Analysing TDMA with slot skipping

We propose a schedulability analysis for a particular class of time division multiple access (TDMA) networks, which we label as TDMA/SS. SS stands for slot skipping, reflecting the fact that a slot is skipped whenever it is not used. Hence, the next slot can start earlier in benefit of hard real-time traffic. In the proposed schedulability analysis, we assume knowledge of all message streams in the system, and that each node schedules messages in its output queue according to a rate monotonic policy (as an example). We present the analysis in two steps. Firstly, we address the case where a node is only permitted to transmit a maximum of one message per TDMA cycle. Secondly, we generalise the analysis to the case where a node is assigned a budget of messages per TDMA cycle it may transmit. A simple algorithm to assign budgets to nodes is also presented

Minimizing System Modification in an Incremental Design Approach

In this paper we present an approach to mapping and scheduling of distributed embedded systems for hard real-time applications, aiming at minimizing the system modification cost. We consider an incremental design process that starts from an already existing system running a set of applications. We are interested to implement new functionality so that the already running applications are disturbed as little as possible and there is a good chance that, later, new functionality can easily be added to the resulted system. The mapping and scheduling problem are considered in the context of a realistic communication model based on a TDMA protocol

Vulnerability Analysis and Mitigation of Directed Timing Inference Based Attacks on Time-Triggered Systems

Much effort has been put into improving the predictability of real-time systems, especially in safety-critical environments, which provides designers with a rich set of methods and tools to attest safety in situations with no or a limited number of accidental faults. However, with increasing connectivity of real-time systems and a wide availability of increasingly sophisticated exploits, security and, in particular, the consequences of predictability on security become concerns of equal importance. Time-triggered scheduling with offline constructed tables provides determinism and simplifies timing inference, however, at the same time, time-triggered scheduling creates vulnerabilities by allowing attackers to target their attacks to specific, deterministically scheduled and possibly safety-critical tasks. In this paper, we analyze the severity of these vulnerabilities by assuming successful compromise of a subset of the tasks running in a real-time system and by investigating the attack potential that attackers gain from them. Moreover, we discuss two ways to mitigate direct attacks: slot-level online randomization of schedules, and offline schedule-diversification. We evaluate these mitigation strategies with a real-world case study to show their practicability for mitigating not only accidentally malicious behavior, but also malicious behavior triggered by attackers on purpose

Diseño de un software de intermediación de comunicación para sistemas distribuidos de tiempo real críticos en Java

Las facilidades e independencia de plataforma de Java han generado un gran interés en la comunidad de tiempo real. Dicho interés se ha reflejado en la especificación RTSJ (Real-Time Specification for Java), que extiende y adapta el lenguaje Java para permitir el desarrollo de sistemas de tiempo real. Adicionalmente, se han desarrollado perfiles de RTSJ para garantizar la predecibilidad en sistemas de tiempo real críticos. Sin embargo, RTSJ y sus perfiles no proporcionan facilidades para sistemas distribuidos. El objetivo de este trabajo es afrontar dicha limitación definiendo un nuevo modelo de RMI (Remote Method Invocation) basado en los principales perfiles de RTSJ para sistemas de tiempo real crítico. Este trabajo presenta el diseño y la implementación de RMI-HRT (RMI-Hard Real-Time) que está enfocado a sistemas de tiempo real crítico con requisitos de alta integridad

Flexibility Driven Scheduling and Mapping for Distributed Real-Time Systems

In this paper we present an approach to mapping and scheduling of distributed hard real-time systems, aiming at improving the flexibility of the design process. We consider an incremental design process that starts from an already existing system running a set of applications, with preemptive priority based scheduling at the process level, and time triggered static scheduling at the communication level. We are interested to implement new functionality so that the already running applications are disturbed as little as possible and there is a good chance that, later, new functionality can easily be added to the resulted system. The mapping and scheduling problems are considered in the context of a realistic communication model based on a TDMA protocol. Extensive experiments as well as a real life example demonstrate the relevance of this problem and the efficiency of our solutions. 1