Overview and timing performance of IEEE 802.1AS

IEEE 802.1AS is being developed in the 802.1 working group as part of a set of standards for audio/video bridging (AVB). AVB networks will carry time-sensitive, high-quality, audio/video traffic, and IEEE 802.1AS will provide synchronization for these networks and ensure that the jitter, wander, and synchronization requirements for the time-sensitive traffic can be met. IEEE 802.1AS includes an IEEE 802-specific layer 2 profile of IEEE Std 1588^TM-2008, plus additional requirements needed to ensure performance for both full-duplex 802.3 (Ethernet) and 802.11 (WiFi) networks. The standard provides for very few options, both to simplify the configuration and operation by the user and to result in low cost. At present, the major features and requirements of 802.1AS are decided, with planned completion by 1Q2009. This paper gives an overview of the 802.1AS standard, describing which features of IEEE Std 1588^TM-2008 it uses and what additional requirements it contains. The paper then describes performance testing that is in progress using early implementations of IEEE 802.1AS bridges and end stations.