Zero Jitter for Deterministic Networks Without Time-Synchronization

Abstract

The demands for deterministic network services are getting significant. IEEE Time sensitive networking (TSN) task group has aimed for deterministic services through IEEE 802 networks. TSN's solutions rely on the time-synchronization and the slot scheduling coordinated throughout a network. The former requires costly hardware implementations for accuracy and scalability. The latter requires a schedulability analysis, which is proven to be NP-complete and not scalable. For modest-to-large scale dynamic networks, a more flexible solution is necessary. We propose a scalable framework that guarantees any desired jitter upper bound, including zero jitter. The framework is composed of; packets with relative time-stamps, a network that guarantees latency bounds, and buffers at the network egress. The latency bounds of a network can be of any value. The buffer holds packets for predetermined intervals to reproduce arbitrary inter-arrival intervals to inter-departure intervals, based on the network's latency bound. The idea behind the proposed framework is to minimize the latency first with work-conserving schedulers, and then adjust the jitter at the egress of a network. We argue that this is simpler than minimizing latency and jitter at the same time. A direct benefit of such simplicity is its scalability. We examine the network solutions that guarantee latency bound, such as the DiffServ and the Flow aggregate-interleave regulator (FAIR), as the candidates for the component in the framework. We show with a case study and simulations that the proposed framework can guarantee smaller latency bounds, with zero jitter, than those of the TSN's synchronous approach.