White-Rabbit -> Data Delivery
Data delivered over White Rabbit network is divided into:
- Best Effort data - as in any standard Ethernet network
- Critical data - unlike in a standard Ethernet network, a White
Rabbit Network provides
- methods to ensure determinism of data delivery (already in current release)
- methods to increase reliability of data delivery (still under development)
Complementary to network methods, the sending and receiving nodes can
apply Forward Error Correction (FEC) to further increase the reliability
of data delivery.
See Methods to Increase Reliability and Ensure Determinism in a White
Rabbit Network (Maciej Lipinski) for
details.
White Rabbit provides delivery of critical data
- with guaranteed upper bound latency
- in a deterministic way
- transparently to "standard" (best effort) data delivery, i.e. the send "standard" traffic can be still sent while critical data is sent, in that case the "standard" traffic may experience higher loss-rate and latency.
White Rabbit critical data delivery is a combination of
- standard solutions (802.1Q priorities, VLANs, Quality of Service)
- hardware support to standard solutions
- Forward Error Correction techniques (not yet implemented)
White Rabbit critical data delivery method is
- a network-wide effort (it affects switches and nodes)
- compatible with standard Ethernet and interoperable with standard Ethernet gear
Short description of critical data delivery in a White Rabbit Network
The critical data distributed over the White Rabbit Network (WRN) is the one sent by a privileged controller node (Data Master) in the payload of the Ethernet frame(s) which needs to be delivered to the nodes-to-be-controlled in a deterministic and reliable way. Therefore, the Data Distribution in the WRN is broken into:
- Critical Data - requires deterministic and reliable delivery
- Standard Data - non-critical, best effort delivery
The reliability of the White Rabbit Network depends on the successful delivery of the Critical Data to all the designated nodes. The worst-case upper bound of its delivery latency from the Data Master to any node in the network, regardless of its location (maximum distance from the Data Master), is required to be guaranteed by the network – this is a determinism requirement. Extremely low critical data loss (i.e. 1 frame per year) is required to be guaranteed by the network - this is a reliability requirement.
Detailed description of robustness in White Rabbit:
- PhD thesis by Maciej Lipinski (2016):
- A presentation about critical data delivery (including use cases of two future applications, 2012)
- An article about robustness in White Rabbit (2011)
- Very detailed descriptions of the ideas (2011):
Status
| Date | Event |
|---|---|
| 10-10-2011 | Initial ideas of methods to ensure determinism, increase reliability of WR network and increase reliability of data transmission presented at ICALEPCS2011 |
| 08-08-2014 | Methods to ensure determinism of WR network: included in the release of the WR switch (described later in PhD by Maciej Lipinski) |
| 04-04-2017 | Methods to increase reliability of WR network: proposed, implemented and tested in PhD by Maciej Lipinski . Not yet in the release of the WR switch. |
Methods to increase reliability of data transmission: to be implemented, possibly in 2017-2018
03 July 2017