Time-sensitive Software-defined Network (TSSDN) for Real-time Applications

Cyber-physical systems (CPS), like the ones used in industrial automation systems, are highly time-sensitive applications demanding zero packet losses along with stringent real-time guarantees like bounded latency and jitter from the underlying network for communication. With the proliferation of IEEE 802.3 and IP networks, there is a desire to use these networks instead of the currently used field-buses for time-sensitive applications. However, these networking technologies, which originally were designed to provide best effort communication services, lack mechanisms for providing real-time guarantees. In this paper, we present Time-Sensitive Software-Defined Networks (TSSDN), which provide real-time guarantees for the time-triggered traffic in time-sensitive systems while also transporting non-time-sensitive traffic. TSSDN provides these guarantees by bounding the non-deterministic queuing delays for time-sensitive traffic. To this end, it exploits the logical centralization paradigm of software-defined networking to compute a transmission schedule for time-sensitive traffic initiated by the end systems based on a global view. In particular, we present various Integer Linear Program (ILP) formulations that solve the combined problem of routing and scheduling time-triggered traffic. Moreover, we show that end systems can comply with a given schedule with high precision using user-space packet processing frameworks. Our evaluations show that TSSDN has deterministic end-to-end delays (≤ 14 μs on our benchmark topology) with low and bounded jitter (≤ 7 μs).