A Verifiable Language for Programming Real-Time Communication Schedules

Abstract

Distributed hard real-time systems require predictable communication at the network level and verifiable communication behavior at the application level. At the network level, communication between nodes must be guaranteed to happen within bounded time and one common approach is to restrict the network access by enforcing a time-division multiple access (TDMA) schedule. At the application level, the application's communication behavior should be verified to ensure that the application uses the predictable communication in the intended way. Network Code is a domain-specific programming language to write a predictable verifiable distributed communication for distributed real-time applications. In this paper, we present the syntax and semantics of Network Code, how we can implement different scheduling policies, and how we can use tools such as model checking to formally verify the properties of Network Code programs. We also present an implementation of a runtime system for executing Network Code on top of RTLinux and measure the overhead incurred from the runtime system. 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.

Hardware Acceleration for Conditional State-Based Communication Scheduling on Real-Time Ethernet

“…We can implement such a framework in two ways: in software and in hardware. Commercially available and research systems [8], [10]- [13], [19]- [22] would allow us to implement it in software on top of it-this has already been done [18] and the driver resides in the network driver of a real-time Linux system using standard Ethernet. This provides good flexibility, because the software can easily be changed and extended to accommodate new features.…”

“…1 provides evidence that implementing the framework on top of standard components introduces high jitter in a system-data comes from tests using the software prototype [18]. Let us consider the instruction which enqueues a message in the output queue.…”

“…Network Code programs of a certain structure remain verifiable [18], analyzeable [27], and composable [28]. Furthermore, Network Code and its runtime can be seen as a programmable communication layer [29].…”

“…Messages sent using the guaranteed quality class have bounded communication delays. We can apply static verification [18] and analysis [27] to compute bounds on communication delays as long as the traffic follows a well-defined temporal pattern.…”

“…State-based schedules based on automata [16] or more explicitly state chart like formalisms with conditional transitions [17], [18] represent recent development to improve scheduling of real-time systems. The Network Code language permits developers to express such conditional state-based communication schedules, and while the specification, analysis, and verification are already partially examined, the systems side of how to efficiently realize such schedules is not yet sufficiently explored as we will show in the following section.…”