DISTRIBUTED TIMING

A key benefit of AVB/TSN is the synchronization of networked devices, which is enabled by gPTP – the generalized Precision Time Protocol. The gPTP standard (IEEE 802.1AS) was developed by the AVB Task Group and released by the IEEE in 2011. The synchronization afforded by gPTP provides a common time base needed for professional-quality clocking of audio and video as well as time-sensitive streams such as industrial robotic controls.

AVB/TSN utilize distributed timing. gPTP nodes periodically exchange packets with embedded timing information with the end result that all gPTP nodes are synchronized to the gPTP grandmaster. The gPTP grandmaster is a single device that is either automatically selected with gPTP’s Best Master Clock Algorithm or manually pre-assigned when so desired. Either way, the end result is the same – precise synchronization (+/- 500ns) of all gPTP nodes.

This level of synchronization is the underpinning that enables protocols built on gPTP (e.g., AVTP) to subsequently synchronize media clocks of talkers and listeners with uncompromised professional quality. Better synchronization also gives major benefits across a variety of cyber physical systems.

Because the timing information is distributed to all nodes, clocking in AVB/TSN is very resilient with features for automatic changeover to a secondary grandmaster should the first one fail and even full grandmaster redundancy.

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