White Rabbit Standardization
Introduction
White Rabbit* (WR) is a protocol developed to synchronize nodes in a
packet-based network with sub-ns accuracy.
The protocol results from the combination of IEEE1588-2008 (Precision
Time Protocol, PTP) with two further extensions:
- automatic precise measurement of the link delay and
- clock syntonization over the physical layer (similar to SyncE).
White Rabbit evolved into an extension of the Precision Time Protocol (PTP) and is therefore referred to as WRPTP. WRPTP is fully compatible with PTP and is currently being defined as a PTP Profile.
The solutions included in WRPTP are now being evaluated by the P1588 Working Group to be included into the next revision of the PTP standard.
White Rabbit Specification (WR Spec)
The White Rabbit Protocol is defined in the White Rabbit Specification (WR Spec) that describes:
- hardware requirements for implementing WRPTP
- protocol requirements for WRPTP-compatibility
White Rabbit Specification material
- WR Specifications
- WR Specification - latest version
- older versions of the WR Spec (to show how the WR Spec evolved)
- short information regarding different versions (i.e. feedback, comments, diffs)
- issues and possible improvements to the current version
Standardization benefits and paths
Standardizing White Rabbit is unquestionably beneficial to the project and is expected to bring a substantial boost to the number of WR applications.
Advantages of standardization:
- easier co-operation with companies
- increase of stability, viability and credibility of the White Rabbit solution
- feedback of experts that enables to polish the solution and make it more mature
Standardization is a considerably long process that can be approached in various ways and from various directions. Potential paths (see presentation) for WR's standardization had been identified. These included:
-
Standardization at the International Telecommunication Union-
Telecommunication Standardization Sector
(ITU-T)
- within Telecom Profile (G.827x) - currently being developed
- as a separate Profile (similar to Telecom)
-
Standardization at the Institute of Electrical and Electronics
Engineers (IEEE)
- as an IEEE1588 PTP Profile
- included into version 3 of PTP (PTPv3) (this is the chosen way of WR standardization)
- as a part of AVB Gen2, included in updated 802.1AS
- Standardization within another standardization body/consortium
White Rabbit standardization within the IEEE1588 revision process
Including White Rabbit into the IEEE1588 (PTP) standard has been
identified as the best and feasible WR standardization path.
White Rabbit was proposed to be included into PTP as a High Accuracy
Option/Profile
(presentation,
document)
at the Special Session of
ISPCS2012. This Special Session
showed an interest and need for reasonably broad IEEE1588 revision. The
first step in revising PTP was the preparation of Project Authorization
Request (PAR) by a Study Group at the beginning of 2013. The PAR states
that the revised protocol "enhances support for synchronization to
better than 1 nanosecond" which reflects the enthusiasm of the group to
evaluate White Rabbit extensions.
The revision process of the IEEE1588 Precision Time Protocol (PTP) standard started in mid-2013. The revision work is done by the P1588 Working Group, which consists of over 180 members from all over the world representing industry and science, including CERN. The Working Group is arranged in 5 sub-committees focusing on different aspects of the PTP revision, namely: Architecture, Management, Upkeep, Security and High Accuracy Enhancements. The High Accuracy sub-committee is lead by CERN representative. It is dedicated to evaluating White Rabbit solutions and generalizing them to a broader range of applications.
Goal of this project
The ultimate goal of this project is to standardize the White Rabbit Protocol.
Project plan
- Evaluation of standardization path/method
- _White Rabbit Standardization Group_ established
to help in evaluation (the end of April 2012):
- representatives of Scientific Institutes (e.g. CERN, GSI) and companies (e.g. NI)
- members of WR Collaboration and external experts
- the responsibility of the group is to perform the further actions
- Each potential path for WR standardization needs to be identified, studied and evaluated
- The most suitable path (in terms of costs, efforts, time) decided (the end of 2012)
- _White Rabbit Standardization Group_ established
to help in evaluation (the end of April 2012):
- Standardization of White Rabbit within
P1588
- The standardization effort started (February 2013)
- An official standardization of White Rabbit will mark the end of the project
Project's timeline
Task | * End date * | |
1. | Establishment of WR Standardization Group | end of April 2012 |
2. | Potential standardization path evaluation | end of September 2012 |
3. | Decision of standardization path choice | end of 2012 |
4. | Start of standardization efforts | February 2013 |
5. | First face-to-face IEEE1588 Study Group meeting, Washington | April 2013 |
6. | Project Authorization Request (PAR) submitted | May 2013 |
7. | Project Authorization Request (PAR) approved | June 2013 |
8. | P1588 Working Group formalized | August 2013 |
9. | High Accuracy Enhancements sub-committee created | August 2013 |
10. | P1588 Plenary meeting and ISPCS, Lemgo | September 2013 |
11. | P1588 Plenary meeting organized at CERN | April 2014 |
12. | P1588 Plenary meeting and ISPCS, Austin | September 2014 |
13. | P1588 Plenary meeting, San Francisco | January 2015 |
14. | P1588 Plenary meeting, Stockholm | May 2015 |
15. | ... standardizing ... | ... |
--. | New revision of IEEE1588 with High Accuracy Option/Profile published | not later than 2018 |
Maciej Lipinski, 09 April 2015