Cross-domain time synchronization in software-defined time-sensitive networking

The rise of time-sensitive applications with broad geographical scope drives the development of time-sensitive networking (TSN) from intra-domain to inter-domain to ensure overall end-to-end connectivity requirements in heterogeneous deployments. When multiple TSN networks interconnect over non-TSN networks, all devices in the network need to be synchronized by sharing a uniform time reference. However, most non-TSN networks are best-effort. Path delay asymmetry and random noise accumulation can introduce unpredictable time errors during end-to-end time synchronization. These factors can degrade synchronization performance. Therefore, cross-domain time synchronization becomes a challenging issue for multiple TSN networks interconnected by non-TSN networks. This paper presents a cross-domain time synchronization scheme that follows the software-defined TSN (SD-TSN) paradigm. It utilizes a combined control plane constructed by a coordinate controller and a domain controller for centralized control and management of cross-domain time synchronization. The general operation flow of the cross-domain time synchronization process is designed. The mechanism of cross-domain time synchronization is revealed by introducing a synchronization model and an error compensation method. A TSN cross-domain prototype testbed is constructed for verification. Results show that the scheme can achieve end-to-end high-precision time synchronization with accuracy and stability.