White rabbit - sensor/actuator protocol for the CERN LHC particle accelerator

Abstract

A distributed sensor/actuator network for control and monitoring of large-scale structures like the CERN Large Hadron Collider is a challenging problem. Currently, no fieldbus equivalent communication system can provide high accuracy (<1 ns) clock synchronization including very low jitter (<100 ps). Since these values are required for the control of such sites (links up to 10 km) a new layer 2 implementation, called White Rabbit (WR) is proposed. The result is an open and standards based protocol and hardware design using synchronous (optical) Gigabit Ethernet links. This paper describes the first results based on simulation and a demonstrator showing that the required performance values can be met without losing compatibility to existing Ethernet infrastructure. The presented simulation validates the designated protocol specification regarding hard real-time delivery of control messages using packet preemption as well as the performance compared to common priority queuing-based solutions.