Network-Code Machine: Programmable Real-Time Communication Schedules

Fischmeister, Sebastian; Sokolsky, Oleg; Lee, Insup

doi:10.1109/rtas.2006.31

Cited by 9 publications

(16 citation statements)

References 18 publications

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“…The execution semantics of a tree schedule as it is executed in the network layer (see [14]) is as follows: The tree schedule starts execution at v 0 with all clocks set to 0. The variables in V are assigned to some default value by the user.…”

Section: Definition Of a Tree Schedulementioning

confidence: 99%

“…If one node transmits a new value for a variable, then all nodes use this new value for evaluating enabling conditions. For more details about this, we refer the reader to Fischmeister et al [14].…”

Section: Definition Of a Tree Schedulementioning

confidence: 99%

“…This has been the motivation to introduce the Network Code [14] as a verifiable, executable coordination model for controlling access to a shared communication medium in a distributed real-time system. In some cases, this model of programming communication enables increased throughput by skipping unnecessary communication compared to the standard offline methods [3].…”

Section: Introductionmentioning

confidence: 99%

“…The programs are interpreted by a runtime environment that executes the instructions. Such a runtime environment has been implemented for RTLinuxPro [14], PIC18F2X8X [18], and as an FPGA [20]. One salient aspect of Network Code is that its programs can be translated to formal specifications, which can be model-checked to verify aspects of reliability such as absence of collisions, overhead, schedulability, and integrity (e.g., sender/receiver pairing, content typing, over/underflows) as shown in [14].…”

Section: Introductionmentioning

confidence: 99%

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Composition Techniques for Tree Communication Schedules

Anand

Fischmeister

Lee

2007

19th Euromicro Conference on Real-Time Systems (ECRTS'07)

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A critical resource in a distributed real-time system is its shared communication medium. Unrestrained concurrent access to the network can lead to collisions that reduce the system's reliability. Therefore in this area, one goal is to develop effective models for coordinating and controlling access to the shared medium and its channels.Network Code is a verifiable, executable model for coordinating and controlling access to a shared communication medium in a distributed real-time system. In this paper, we investigate the problem of building an application by composing multiple Network Code programs. To reason about the composition, we model Network Code programs as Tree Schedules (TS) and then consider the composition of schedules that describe how the network is accessed by different applications. Specifically, we first define the notions of compatibility and composability of tree schedules, and then provide algorithms for their composition and reason about overhead of composition. We illustrate the techniques by considering the composition of two control applications. Comments Copyright 2007 IEEE. Reprinted from Proceedings of the 19th Euromicro Conference on Real-Time Systems (ECRTS'07), July 2007, pages 235-246.This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the University of Pennsylvania's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.This conference paper is available at ScholarlyCommons: http://repository.upenn.edu/cis_papers/346 AbstractA critical resource in a distributed real-time system is its shared communication medium. Unrestrained concurrent access to the network can lead to collisions that reduce the system's reliability. Therefore in this area, one goal is to develop effective models for coordinating and controlling access to the shared medium and its channels.Network Code is a verifiable, executable model for coordinating and controlling access to a shared communication medium in a distributed real-time system. In this paper, we investigate the problem of building an application by composing multiple Network Code programs. To reason about the composition, we model Network Code programs as Tree Schedules (TS) and then consider the composition of schedules that describe how the network is accessed by different applications. Specifically, we first define the notions of compatibility and composability of tree schedules, and then provide algorithms for their composition and reason about overhead of composition. We illustrate the techniques by considering the composition of two control applications.

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Section: Definition Of a Tree Schedulementioning

confidence: 99%

Section: Definition Of a Tree Schedulementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Composition Techniques for Tree Communication Schedules

Anand

Fischmeister

Lee

2007

19th Euromicro Conference on Real-Time Systems (ECRTS'07)

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“…To overcome these limitations, we have proposed network code [9], which permits creating application-specific protocols by providing a programmable media access layer. Network code is an executable communication abstraction to specify predictable and verifiable communication for distributed real-time applications.…”

Section: Introductionmentioning

confidence: 99%

An analysis framework for network-code programs

Anand¹,

Fischmeister²,

Lee³

2006

Proceedings of the 6th ACM &Amp; IEEE International Conference on Embedded Software - EMSOFT '06

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Distributed real-time systems require a predictable and verifiable mechanism to control the communication medium. Current real-time communication protocols are typically independent of the application and have intrinsic limitations that impede customizing or optimizing them for the application. Therefore, either the developer must adapt her application and work around these subtleties or she must limit the capabilities of the application being developed.Network Code, in contrast, is a more expressive and flexible model that specifies real-time communication schedules as programs. By providing a programmable media access layer on the basis of TDMA, Network Code permits creating application-specific protocols that suit the particular needs of the application. However, this gain in flexibility also incurrs additional costs such as increased communication and run-time overhead. Therefore, engineering an application with network code necessitates that these costs are analyzed, quantified, and weighted against the benefits.In this work, we propose a framework to analyze network code programs for commonly used metrics such as overhead, schedulability, and average waiting time. We introduce Timed Tree Communication Schedules, based on timed automata to model such programs and define metrics in the context of deterministic and probabilistic communication schedules. To demonstrate the utility of our framework, we study an inverted pendulum system and show that we can decrease the cumulative numeric error in the model's implementation through analyzing and improving the schedule based on the presented metrics. Current real-time communication protocols are typically independent of the application and have intrinsic limitations that impede customizing or optimizing them for the application. Therefore, either the developer must adapt her application and work around these subtleties or she must limit the capabilities of the application being developed. Network Code, in contrast, is a more expressive and flexible model that specifies real-time communication schedules as programs. By providing a programmable media access layer on the basis of TDMA, Network Code permits creating application-specific protocols that suit the particular needs of the application. However, this gain in flexibility also incurs additional costs such as increased communication and run-time overhead. Therefore, engineering an application with network code necessitates that these costs are analyzed, quantified, and weighted against the benefits.In this work, we propose a framework to analyze networkcode programs for commonly used metrics such as overhead, schedulability, and average waiting time. We introduce Timed Tree Communication Schedules, based on timed automata to model such programs and define metrics in the context of deterministic and probabilistic communication schedules. To demonstrate the utility of our framework, we study an inverted pendulum system and show that we can decrease the cumulative numeric error in the model's implementat...

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