• KSII Transactions on Internet and Information Systems
    Monthly Online Journal (eISSN: 1976-7277)

qPALS: Quality-Aware Synchrony Protocol for Distributed Real-Time Systems


Abstract

Synchronous computing models provided by real-time synchrony protocols, such as TTA [1] and PALS [2], greatly simplify the design, implementation, and verification of real-time distributed systems. However, their application to real systems has been limited since their assumptions on underlying systems are hard to satisfy. In particular, most previous real-time synchrony protocols hypothesize the existence of underlying fault tolerant real-time networks. This, however, might not be true in most soft real-time applications. In this paper, we propose a practical approach to a synchrony protocol, called Quality-Aware PALS (qPALS), which provides the benefits of a synchronous computing model in environments where no fault-tolerant real-time network is available. qPALS supports two flexible global synchronization protocols: one tailored for the performance and the other for the correctness of synchronization. Hence, applications can make a negotiation flexibly between performance and correctness. In qPALS, the Quality-of-Service (QoS) on synchronization and consistency is specified in a probabilistic manner, and the specified QoS is supported under dynamic and unpredictable network environments via a control-theoretic approach. Our simulation results show that qPALS supports highly reliable synchronization for critical events while still supporting the efficiency and performance even when the underlying network is not stable.


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Cite this article

[IEEE Style]
Woochul Kang and Lui Sha, "qPALS: Quality-Aware Synchrony Protocol for Distributed Real-Time Systems," KSII Transactions on Internet and Information Systems, vol. 8, no. 10, pp. 3361-3377, 2014. DOI: 10.3837/tiis.2014.10.004

[ACM Style]
Kang, W. and Sha, L. 2014. qPALS: Quality-Aware Synchrony Protocol for Distributed Real-Time Systems. KSII Transactions on Internet and Information Systems, 8, 10, (2014), 3361-3377. DOI: 10.3837/tiis.2014.10.004