The White Rabbit Project

White Rabbit is the name of a collaborative project including CERN, GSI Helmholtz Centre for Heavy Ion Research, and other partners from universities and industry to develop a fully deterministic Ethernet-based network for general purpose data transfer and sub-nanosecond accuracy time transfer. Its initial use was as a timing distribution network for control and data acquisition timing of the accelerator sites at CERN as well as in GSI's Facility for Antiproton and Ion Research (FAIR) project. The hardware designs as well as the source code are publicly available.[1] The name of the project is a reference to the White Rabbit appearing in Lewis Carroll's novel Alice's Adventures in Wonderland.

## Contents

* 1 Focus and goals
* 2 Technologies
* 3 White Rabbit applications
* 4 A White Rabbit timing network
* 5 References
* 6 External links

## Focus and goals

White Rabbit provides sub-nanosecond synchronization accuracy, which formerly required dedicated hard-wired timing systems, with the flexibility and modularity of real-time Ethernet networks. A White Rabbit network may be used solely to provide timing and synchronization to a distributed electronic system, or be used to provide both timing and real-time data transfer.[2][3]

The White Rabbit Project focuses on:

* Sub-nanosecond accuracy: synchronization of more than 1000 nodes via fiber or copper connections of up to 10 km of length.
* Flexibility: creates a scalable and modular platform with simple configuration and low maintenance requirements.
* Predictability and Reliability: allows the deterministic delivery of highest priority messages by using Class of service.
* Robustness: no losses of high priority system device control messages.
* Open source hardware and software: to avoid vendor lock-in.

## Technologies

To achieve sub-nanosecond synchronization White Rabbit utilizes:

* Synchronous Ethernet (SyncE) to achieve syntonization[4] and
* IEEE 1588 (1588) Precision Time Protocol (PTP)

White Rabbit uses the Precision Time Protocol to achieve sub-nanosecond accuracy. A two-way exchange of the Precision Time Protocol synchronization messages allows precise adjustment of clock phase and offset. The link delay is known precisely via accurate hardware timestamps and the calculation of delay asymmetry.

## White Rabbit applications

At CERN White Rabbit was used for the new control system of the injector chain.

At GSI White Rabbit will become the timing system of the FAIR complex.

The KM3NeT neutrino telescope uses White Rabbit for synchronizing the detector units.[5]

Several companies[6] have begun to commercialize White Rabbit for commercial applications by developing their own White Rabbit hardware and software.

The first white rabbit element on the white rabbit project was the "white rabbit switch", financed by The government of Spain and CERN, and produced by Seven Solutions.

In year 2015-2016 White Rabbit was successfully deployed by Project DEMETRA service #3 and tested for distribution Galileo precise UTC using ground fiber service.

## A White Rabbit timing network

In a White Rabbit timing network a designated timing master node provides timing for the entire network. The timing master is syntonized with an atomic clock and is synchronized with a GPS receiver.

Components of a White Rabbit network are multi-port White Rabbit Switches and single or dual-port White Rabbit nodes. Both components may be added dynamically to the network. Cable length and other delay factors are automatically compensated by the Precision Time Protocol algorithms. Though conventional Gigabit Ethernet devices may be connected as well only White Rabbit devices take part in network timing and synchronization.

## References

1. ↑ "White Rabbit Overview". http://www.ohwr.org/projects/white-rabbit. Retrieved 2013-07-18.
2. ↑ The White Rabbit Project. 2009. http://accelconf.web.cern.ch/accelconf/icalepcs2009/papers/tuc004.pdf. Retrieved 2013-07-18.
3. ↑ White rabbit: Sub-nanosecond timing distribution over Ethernet. October 2009. http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5340196&tag=1. Retrieved 2013-07-18.
4. ↑ wikt:syntonization
5. ↑ "KM3NeT - On-line detector control and Data Acquisition". http://www.km3net.org/newsite/research/detector/on-line-detector-control/. Retrieved 2016-01-20.
6. ↑ "Open Hardware Repository Companies". http://www.ohwr.org/companies. Retrieved 2013-07-18.

## External links

* Official website
* White Rabbit Tutorial
* PTTI 2011 paper
* White Rabbit Solution

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