Incremental Routing and Scheduling Using Multipath and Nonzero Jitter Bound for IEEE 802.1 Qbv Time Aware Shaper

IEEE 802.1 Qbv time-aware shaper (TAS) has been developed for delivery of time-critical periodic frames of time-triggered (TT) flows over Ethernet under strict end-to-end latency and jitter bounds. Efficient routing and flow scheduling are critical for successful deployments of TAS systems. Although many routing and flow scheduling schemes for TAS have been proposed so far, most of them are restricted to single path routing and zero jitter delivery. Multipath routing and nonzero jitter bound could provide more flexibility in scheduling thus increase scheduling success. However they have been rarely studied in TAS scheduling. In this work, online incremental routing and scheduling schemes utilizing multipath routing and nonzero jitter bound are proposed based on no-wait packet switching mechanism for TAS. Two routing and scheduling schemes with nonzero jitter bound are proposed, i.e., incremental single path routing and scheduling with nonzero jitter bound (ISPRS-NZJ) and incremental multipath routing and scheduling with nonzero jitter bound (IMPRS-NZJ). Both schemes are based on the proposed resource-centric scheduling approach in which information on feasible free time-slices in the paths for a TT flow is updated according to flow scheduling result and used for scheduling of next flow. Paths for a flow are searched by depth-first way and cumulative free time-slices (CFTSs) in each link of a path are found and used in ISPRS-NZJ. In IMPRS-NZJ, combined cumulative free time-slices (CCFTSs) are obtained from CFTSs and used for scheduling. Numerical results show that scheduling with nonzero jitter bound or multipath routing could reduce schedule failure rates compared with typical single path scheduling with zero jitter bound. Also it is shown that scheduling with nonzero jitter bound is more effective in reducing schedule failure rates than scheduling with multipath routing.