The Audio/Video Bridging project in the IEEE 802.1 working group is focused on the transport of time-sensitive traffic over IEEE 802 bridged networks. Current bridged networks do not have mechanisms that enable meeting these requirements under general traffic conditions. IEEE 802.1AS is the AVB standard that will specify requirements to allow for transport of precise timing and synchronization in AVB networks. It is based on IEEE 1588-2008, includes a PTP profile that is applicable to full-duplex IEEE 802.3 transport, and adds specifications for timing transport over IEEE 802.11, IEEE 802.3 EPON, and CSN media. This article provides a tutorial on IEEE 802.1AS that updates earlier descriptions, and new simulation results for timing performance.