  Deterministic communication is required for applications of several industry
verticals including manufacturing, automotive, financial, and health care, etc.
These applications rely on reliable and time-synchronized delivery of
information among the communicating devices. Therefore, large delay variations
in packet delivery or inaccuracies in time synchronization cannot be tolerated.
In particular, the industrial revolution on digitization, connectivity of
digital and physical systems, and flexible production design require
deterministic and time-synchronized communication. A network supporting
deterministic communication guarantees data delivery in a specified time with
high reliability. The IEEE 802.1 TSN task group is developing standards to
provide deterministic communication through IEEE 802 networks. The IEEE 802.1AS
standard defines time synchronization mechanism for accurate distribution of
time among the communicating devices. The time synchronization accuracy depends
on the accurate calculation of the residence time which is the time between the
ingress and the egress ports of the bridge and includes the processing,
queuing, transmission, and link latency of the timing information. This paper
discusses time synchronization mechanisms supported in current wired and
wireless integrated systems.
