White rabbit: a PTP application for robust sub-nanosecond synchronization

This article describes time distribution in a White Rabbit Network. We start by presenting a short overview of the White Rabbit project explaining its requirements to highlight the importance of the timing aspects of the system. We then introduce the technologies used to achieve high clock accuracy, stability and resilience in all the components of the network. In particular, the choice of the IEEE 1588-2008 (PTP) and Synchronous Ethernet standards are explained. In order to accommodate hardware-supported mechanisms to increase PTP synchronization accuracy, we introduce the White Rabbit extension to PTP (WRPTP). The hardware used to supportWRPTP is presented.Measured results of WRPTP performance demonstrate sub-nanosecond accuracy over a 5km fiber optic link with a precision below 10ps and a reduced PTP-message exchange rate. Tests of the implementation show full compatibility with existing PTP gear.