White Rabbit (WR) is a solution to the generic problem of transferring
data in a fast, deterministic and safe manner. Although its initial
scope is mainly targeted at timing systems for experimental physics
facilities, care has been taken to come up with a solution which is as
generic as possible. White Rabbit is able to synchronize ~1000 nodes
with sub-ns accuracy over fiber lengths of up to 10 km. The main
technologies used are physical layer syntonization (clock recovery) and
PTP (IEEE 1588). Compliance with established standards such as Ethernet
and PTP is a key goal of the project.
The White Rabbit project is an on-going collaborative project for which
first generation components have been designed and evaluated for use in
real, mostly scientific, applications. The list of users is
expanding rapidly with metrological institutes and astronomical
observation centres evaluating White Rabbit.
The hardware design for the White Rabbit switch is licensed under the
CERN Open Hardware Licence
while the firmware and driver software also is available under "open"
White Rabbit overview
White Rabbit (WR) is an extension to Ethernet technology developed in
collaboration with many institutes and companies. It allows users to
synchronize remote pieces of equipment to within one billionth of a
second (1 nanosecond).
The project is completely based on free software and Open Source
Hardware. Users of WR technology can purchase equipment from commercial
vendors. This combination of open source and commercial approaches
allows users to build on top of well-supported solutions without any
risk of vendor lock-in.
WR benefits from a vibrant diverse community of developers and users.
Because many eyes look at designs, bugs get identified early and fixed
promptly. Also, as often happens with open source developments, WR has
found uses in areas which are very removed from accelerator control
systems. Groups in the Netherlands and Finland are exploring ways of
using WR to disseminate official time. They have therefore contributed
to the WR effort in order to extend its range from the few km into the
hundreds of km realm. Other groups have developed extremely robust WR
hardware because they need it to operate in extreme conditions. One
example is the WR-based timing system of the HiSCORE Gamma and Cosmic
Ray detector in the Tunka valley in Siberia. The KM3NeT neutrino
detector provides for an even more dramatic setting: WR nodes have been
recently deployed 100 km into Mediterranean Sea off the coast of Italy,
at a water depth of 3500 m.
Precise network synchronization is a very active area of development
worldwide. Recognizing the performance benefits of WR technology, the
IEEE 1588 working group is currently working on a new revision of the
standard which includes an effort to take concepts from WR. This will
allow the IEEE 1588 standard to tackle synchronization applications in
the nanosecond realm.