Time-triggered (TT) switched networks are a deterministic communication infrastructure used by real-time distributed embedded systems. These networks rely on the notion of globally discretized time (i.e. time slots) and a static TT schedule that prescribes which message is sent through which link at every time slot, such that all messages reach their destination before a global timeout. These schedules are generated offline, assuming a static network with fault-free links, and entrusting all error-handling functions to the end user. Assuming the network is static is an over-optimistic view, and indeed links tend to fail in practice. We study synthesis of TT schedules on a network in which links fail over time and we assume the switches run a very simple error-recovery protocol once they detect a crashed link. We address the problem of finding a pk; qresistant schedule; namely, one that, assuming the switches run a fixed error-recovery protocol, guarantees that the number of messages that arrive at their destination by the timeout is at least no matter what sequence of at most k links fail. Thus, we maintain the simplicity of the switches while giving a guarantee on the number of messages that meet the timeout. We show how a pk; q-resistant schedule can be obtained using a CEGAR-like approach: find a schedule, decide whether it is pk; q-resistant, and if it is not, use the witnessing fault sequence to generate a constraint that is added to the program. The newly added constraint disallows the schedule to be regenerated in a future iteration while also eliminating several other schedules that are not pk; q-resistant. We illustrate the applicability of our approach using an SMT-based implementation.
|Title of host publication||Proceedings of the 13th International Conference on Embedded Software, EMSOFT 2016|
|Publisher||Association for Computing Machinery, Inc|
|State||Published - 1 Oct 2016|
|Event||13th International Conference on Embedded Software, EMSOFT 2016 - Pittsburgh, United States|
Duration: 1 Oct 2016 → 7 Oct 2016
|Name||Proceedings of the 13th International Conference on Embedded Software, EMSOFT 2016|
|Conference||13th International Conference on Embedded Software, EMSOFT 2016|
|Period||1/10/16 → 7/10/16|
Bibliographical notePublisher Copyright:
© 2016 ACM.
- Fault tolerance
- Real-time communication
- Satisfiability Modulo Theory
ASJC Scopus subject areas
- Hardware and Architecture