1. Redundant network topologies for dependable time transfer
Increasing Availability & Fault Tolerance
Jose Luis Gutierrez, Maciej Lipiński, Javier Diaz

2. Redundancy Protocols
PRP & HSR

3. REDUNDANCY PROTOCOLS
PRP
HSR

4. HSR PROTOCOL Main Features:
What is High-availability Seamless Redundancy (HSR)?
HSR (IEC Clause 5) is an Ethernet protocol suited for applications that demand high availability and very short switch over time. It is one of the redundancy protocols selected for substation automation in IEC
It can also be employed in other critical networking applications: industrial automation, motion control and transportation.
The nodes are attached by two Ethernet ports to the ring (same MAC address)
Main Features:
Ring topology
Time & data transfer duplication
Avoids single point of failure
Zero-time recovery
Cheaper than PRP

5. „A“-frame (HSR tagged)
HSR PROTOCOL
source
destinations
„C“-frame
(untagged)
„D“-frame (untagged)
“A” frames
“B” frames
standard frames
removal from the ring
node
CPU
DANH
DANH
„A“-frame (HSR tagged)
„B“-frame
(HSR tagged)
Nodes are arranged as a ring, each node has two identical interfaces, port A and port B.
For each frame to send (“C”-frame), the source node sends two copies over port A and B.
Each node relays a frame it receives from port A to port B and vice-versa, except if it already forwarded it.
The destination nodes consumes the first frame of a pair and discards the duplicate.
In case of interruption of the ring, frames still continue to be received over the intact path. B A
DANH
DANH
DANH
DANH
DANH
destinations

6. HSR PROTOCOL: Node architecture
Redundant Ethernet ports
Link Redundancy Entity (LRE)
Duplicate frames
Drop duplicated frames
HSR tagger
Forwarding frames
HSR table
(dest, orig, HSR nº) …

7. HSR PROTOCOL: How it works
Timing
Rings are formed by Transparent clocks + Ordinary Clocks (TC+OC)
PTP are handled in both ports on each HSR node.
There can be more than 1 Time reference BUT they never work at the same time.

8. WR-HSR Implementation
Road to WR-HSR

9. HSR to White-Rabbit HSR
Adapting HSR to White-Rabbit-HSR
End-to-end mechanism for clock transfer
Delay request for delay estimation
Tree topology
Switchover mechanism in case of failure
Boundary Clocks
Peer-to-Peer for clock transfer
Peer-delay for delay estimation
Ring topology
Switchover to ring topologies
Transparent Clocks
New development for White-Rabbit-HSR
Development of a HSR tag included in time & data frames
Development of gateware/software to duplicate, forward and drop frames
Development of HSR management frames
Enhance holdover of White- Rabbit devices to ease switchover

10. WR PPSi-P2P IMPLEMENTATION
Master
Slave TC CF T1
Sync
Tsync_ingress
Tsync_egress
Follow up
RTMT T2 T1 + CF LD
LDL
LDR LD
Correction Field ( - ) +
Tsync_egress -
Tsync_ingress +
Reception Link Delay
Slave Offset = T2 T1 + CF LD
Residence Time

11. WRS GATEWARE

12. WR-HSR Network P2P PTP Behaviour
Adds a HSR tag and duplicates the frame
In both directions
 Sync
 follow_up
GrandMaster
WR slave
SyncA 
follow_upA 
SyncA 
follow_upA 
 SyncB
 follow_upB
 SyncB
 follow_upB
 Sync
 follow_up
Manages PTP frames in both ports independetly
BMC (A||B)
BMC (A||B)
Sync 
follow_up 
SyncB 
follow_upB 
SyncB 
follow_upB 
Removes HSR tag
 SyncA
 follow_upA
 SyncA
 follow_upA
WR slave
BMC (A||B)
Sync  Non-HSR Sync frame
SyncA HSR-Sync from path A
SyncB HSR-Sync from path B
Sync 
follow_up 
WR slave

13. Single point of failure avoidance
High-Availability: Adding Redundancy Features

14. SWITCHOVER MECHANISM Normal Operation Switch A Failure Detected
 PTP 
Switch A
1-Pulse per Second output (PPS)
switchover
Failure Detected
Switch B
Slave port
Backup port
1-Pulse per Second output (PPS)
Maciej’s switchover:
Slave port: performs the WR-PTP normally
Backup port: stores WR-PTP data but doesn’t apply
After Switchover
When PPS drifts, the WRS starts using the data from the backup port and applies them.
1-Pulse per Second output (PPS)

15. WR-HSR Development status
Presentation title
WR-HSR Development status
PeerDelay mechanism: measures the link delay between two adjacent nodes. (100%)
Peer-to-Peer mechanism:
Boundary Clock implementation: Middle nodes are syntonized and synchronized with master. (100%)
Transparent Clock implementation: Middle nodes are syntonized but not synchronized with master. (100%)
HSR Tagging/untagging
For timing: 100%
For data: 25% (gateware approach )
Switchover mechanism: In case of failure, all nodes switch the path from where they get syntonized/synchronized. (75% adding more WRSs)
Holdover enchancement: Probabilistic model to increase current WRS holdover to make possible the switchover mechanism (~100ms).
Copyright © Infineon Technologies All rights reserved.

16. WR-HSR Development TESTS
Presentation title
WR-HSR Development TESTS
Frequency distribution in the ring
Number of ring nodes (max?)
Holdover < switchover GM GM GM S S S S S S S S S S
Mínimum test case S
Copyright © Infineon Technologies All rights reserved.

17. Generic Substation Events (GSE)
TOWARDS SMART GRID
Generic Substation Events (GSE)
GOOSE (Generic Object Oriented Substation Events)
GSSE (Generic Substation State Events).
SMV (Sampled Measured Values)
The IEC standard for substation enables the integration of all protection, control, measurement and monitoring functions. These functions require high speed and reliable communication in the substation
For mission-critical or time-sensitive applications, even millisecond long network interruptions cannot be tolerated
IEC states that the time that the plant allows for recovery before taking emergency actions (e.g., emergency shut-down, fall-back mode) should be less than 10 ms.
IEC v2 clearly states that the communication redundancy times of GOOSE and SMV protocols in substation automation systems are required to be BUMPLESS (i.e., have a zero switch-over time).

18. TOWARDS SMART GRID
Communication profiles of protocols used in IEC61850

19. WR-HSR links
White-Rabbit HSR project:
Ported to Silicon PTP – PPSi (PTPv2) for White-Rabbit:
White Rabbit Switch Software:
White Rabbit Switch Gateware:
White Rabbit Cores:
IEC 61850: Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems
IEC 62439: High Availability Automation Networks

20. Thanks for your attention