Hardware acceleration for verifiable, adaptive real-time communication (original) (raw)
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IEEE Transactions on Computers, 1998
Abstract| Parallel machines have the potential to satisfy the large computational demands of real-time applications. These applications require a predictable communication network, where time-constrained tra c requires bounds on throughput and latency while good average performance su ces for best-e ort packets. This paper presents a new router architecture that tailors low-level routing, switching, arbitration, ow-control, and deadlock-avoidance policies to the con icting demands of each tra c class. The router implements bandwidth regulation and deadline-based scheduling, with packet switching and table-driven multicast routing, to bound end-to-end delay and bu er requirements for time-constrained tra c, while allowing best-e ort trafc to capitalize on the low-latency routing and switching schemes common in modern parallel machines. To limit the cost of servicing time-constrained tra c, the router includes a novel packet scheduler that shares link-scheduling logic across the multiple output ports, while masking the e ects of clock rollover on the represention of packet eligibility times and deadlines. Using the Verilog hardware description language and the Epoch silicon compiler, we demonstrate that the router design meets the performance goals of both tra c classes in a single-chip solution. Verilog simulation experiments on a detailed timing model of the chip show how the implementation and performance properties of the packet scheduler scale over a range of architectural parameters.
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Polytechnic Institute of Porto …, 2000
Ethernet is the most popular LAN technology. Its low price and robustness, resulting from its wide acceptance and deployment, has created an eagerness to expand its responsibilities to the factory-floor, where real-time requirements are to be fulfilled. However, it is difficult to build a real-time control network using Ethernet, because its MAC protocol, the 1-persistent CSMA/CD protocol with the BEB collision resolution algorithm, has unpredictable delay characteristics. Many anticipate that the recent technological advances in Ethernet such as the emerging Fast/Gigabit Ethernet, micro-segmentation and full-duplex operation using switches will also enable it to support time-critical applications. This technical report provides a comprehensive look at the unpredictability inherent to Ethernet and at recent technological advances towards real-time operation. 1
A Fault-Tolerant Ethernet for Hard Real-Time Adaptive Systems
IEEE Transactions on Industrial Informatics
Distributed embedded systems (DESs) that perform critical tasks in unpredictable environments must be reliable, hard real-time, and adaptive. Since a DES comprises nodes that rely on a network, the network must provide adequate support: it must be reliable, convey messages on time, and meet new realtime requirements as the nodes adapt. Ethernet is ill-suited for such hard real-time adaptive systems, but it can be made suitable. The Flexible Time-Triggered (FTT) paradigm already supports hard real-time message exchanges and the necessary flexibility to meet evolving hard real-time requirements, but its Ethernet implementations had reliability limitations. To address these, we designed FTTRS, a communication subsystem that tolerates permanent and transient faults, even if they occur simultaneously, while keeping the paradigm's key features: support for both the timely exchange of periodic and sporadic real-time messages, and support for updating the real-time parameters of these messages at runtime. In this paper we present FTTRS, the first Ethernetbased communication subsystem specifically designed for highly reliable hard real-time adaptive DESs.
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This paper presents the design and implementation of RT-EP (Real-Time Ethernet Protocol), which is a softwarebased token-passing Ethernet protocol for multipoint communications in real-time applications, that does not require any modification to existing Ethernet hardware. This protocol allows the designer to model and analyze the real-time application using it, because it is based on fixed priorities and well-known schedulability analysis techniques can be applied. Furthermore, this protocol provides the applications the capacity of recovering from some fault conditions. It has been ported to an implementation of the Minimal Real-Time POSIX standard called MaRTE OS.
RT-EP: A Fixed-Priority Real Time Communication Protocol over Standard Ethernet
Lecture Notes in Computer Science, 2005
This paper presents the design and implementation of RT-EP (Real-Time Ethernet Protocol), which is a software-based token-passing Ethernet protocol for multipoint communications in real-time applications, that does not require any modification to existing Ethernet hardware. The protocol allows a fixed priority to be assigned to each message, and consequently well-known schedulability analysis techniques can be applied. A precise model of its timing behavior has been obtained. Furthermore, this protocol provides the ability of recovering from some fault conditions. It has been ported to an implementation of the Minimal Real-Time POSIX standard called MaRTE OS [10], and is being used to support real-time communications in an implementation of Ada's Distributed Systems Annex (RT-GLADE). It has been successfully used to implement a distributed controlled for an industrial robot.
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Adaptive real-time systems can respond to changes in the environment and thus allow for an extended range of oper-ations and for improved efficiency in the use of system resources. Building such adaptive real-time systems requires flexibility at each layer in the system stack. In this paper, we introduce and discuss our on-going effort to build a programmable arbitration layer. It builds on the Network Code language and enables the developer to program application-specific arbitration mechanisms which optimize bandwidth or encodes specific properties such as data redundancy, collision-free communication, and temporal isolation.