TIME SYNCHRONIZATION AND COMMUNICATION IN … · IEEE 802.1AS-REV EXAMPLE Page 11 Among other...
Transcript of TIME SYNCHRONIZATION AND COMMUNICATION IN … · IEEE 802.1AS-REV EXAMPLE Page 11 Among other...
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
TIME SYNCHRONIZATION AND COMMUNICATION IN REDUNDANT NETWORKS
IEEE ETHERNET & IP @ AUTOMOTIVE TECHNOLOGY DAY
DETROIT, SEPTEMBER 2019
THORSTEN HOFFLEIT
AUTOMOTIVE NETWORKING COMPETENCE CENTER
AUTOMOTIVE SOLUTION BUSINESS UNIT
RENESAS ELECTRONICS CORPORATION
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
AGENDA
Page 2
▪ Need for redundancy & time synchronization
▪ Operation of IEEE 802.1CB (Frame replication and elimination for redundancy)
and effects in case of package loss/ link loss
▪ Alternative approach to IEEE 802.1CB
▪ Improvements coming up in IEEE 802.1AS
(Timing and Synchronization for Time sensitive Applications)
▪ Summary and conclusion
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
IN VEHICLE CONNECTIVITYMOVE TOWARDS ZONE-BASED ARCHITECTURE WITH ETHERNET BACKBONE
Page 3
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
IN VEHICLE CONNECTIVITYMOVE TOWARDS ZONE-BASED ARCHITECTURE WITH ETHERNET BACKBONE
Page 4
▪ New E/E architectures will use Ethernet as backbone
▪ Limited bandwidth and latency are constraints
▪ Reliable service oriented communication is key
▪ Mechanisms are required to guarantee data delivery
▪ IEEE 802.1CB
▪ IEEE802.1AS-rev
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
IEEE 802.1CBEXAMPLE CRITICAL STREAMS
Page 5Page 5
Talker Listener
Listener
Sequence generation function
Individual recovery function/ stream splitting
Sequence recovery function
Stream identification
Every stream from a talker
undergoes identification function
Examines sequence numbers and
discards duplicates from single
ingress port. Duplicate frames if
needed to all configured outputs.
Examines sequence numbers
and discards duplicates from
different ingress ports.
Finally only one package is
received by listener system and
removes sequence number
At talker side two “identical”
packages are created (member
streams). “R-Tag” with sequence
number is added.
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
IEEE 802.1CBSYSTEM CONTEXT
Page 6
▪ Failure models in IEEE 802.1CB
▪ Frame loss
▪ Link loss
▪ Stuck transmitter
▪ Ring architecture also supports component
failure
▪ Redundant path keeps communication
ongoing
▪ Additional system countermeasures required
▪ Redundancy does not come for free
▪ Architectural considerations
▪ Additional cables
▪ Additional ports
▪ Increased communication traffic
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
SEQUENCE ORDERINGCHALLENGE FOR APPLICATION
Page 7
Challenges:
▪ Package disordering (depends on traffic type )
▪ History list depth
T1 T2 T3 T4 T5 T6
T1’ T2’ T4’ T5’ T6’
T
A
T1’’ T2’’ T3’’ T4’’ T5’’ T6’’B
CC
T7
T7’
T7’’
D T1’’’ T2’’’ T3’’’ T4’’ T5’’ T6’’C
L T1’ T2’ T4’ T5’ T6’ T3’’’ T7’
T L
A
BD
C
Countermeasures:
▪ Avoid bursts by using shapers/ use preemption
▪ Reorder sequence with help of sequence numbers in transport layer
▪ Accept disordered packages and solve in application layer
T3’ CB bridge
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019Page 8
ALTERNATIVE APPROACH –VLAN SPLITTING
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019Page 9
▪ Characteristics
▪ Talker and listener are responsible for replication
and elimination in software
▪ Increased traffic on joint paths
▪ Bridges can be realized with standard products
▪ No guaranteed interoperability
− E.g. special redundancy layer in stack
− Redundancy aware application
− Everything vendor specific
ALTERNATIVE APPROACH –VLAN SPLITTING
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
COMPARISONIEEE 802.1CB VS. VLAN BASED REDUNDANCY
Page 10
▪ IEEE 802.1CB
▪ Special hardware required in bridges
▪ Endpoints can handle in software with low effort
▪ Tooling support for bridge configuration
▪ Standard, industry will support
▪ VLAN based approach software based
▪ No special hardware features required
▪ Can tune requirements of application (disordering)
▪ Increased traffic on joint paths
▪ No guaranteed interoperability
▪ Same failure modes
▪ Same targets achievable with both methods
▪ Both methods are applicable for routable protocols only
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
REDUNDANCY FOR LINK-BASED PROTOCOLSIEEE 802.1AS-REV EXAMPLE
Page 11
▪ Among other improvements, changes were done with respect to reliability of synchronization
▪ Redundancy and reliability considerations in IEEE 802.1AS-rev
▪ Multiple timing domains
▪ Multiple “active” grand masters (GM)
▪ Smooth transition from one GM to another
▪ Improved failure detection mechanisms
▪ Slave port monitoring
▪ To operate these features, devices in system needs to support new standard
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
REDUNDANCY FOR LINK-BASED PROTOCOLSIEEE 802.1AS-REV REDUNDANT PATH
Page 12
Principle:
▪ One clock source used for multiple domains
▪ Link redundancy
Clock master
gPTP
gPTP
Clock slave
gPTP
gPTP
gPTP
gPTP
Clock slave
Notes
▪ GM single point of failure
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
REDUNDANCY FOR LINK-BASED PROTOCOLSIEEE 802.1AS-REV REDUNDANT SOURCE
Page 13
Clock master
gPTP
Clock master
(standby)
gPTP
gPTP
gPTP
gPTP gPTP
Clock slave
Principle:
▪ Independent back-up GM (hot standby)
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
REDUNDANCY FOR LINK-BASED PROTOCOLSIEEE 802.1AS-REV REDUNDANT SOURCE
Page 14
Clock master
gPTP
Clock master
(standby)
gPTP
gPTP
gPTP
gPTP gPTP
Clock slave
Principle:
▪ Independent back-up GM (hot standby)
▪ Two independent timing domains
Notes
▪ Link failure would split into two independent
timing domains (no link redundancy)
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
REDUNDANCY FOR LINK-BASED PROTOCOLSIEEE 802.1AS-REV REDUNDANT PATH & SOURCE
Page 15
Clock master
gPTP
gPTP
Clock master
(standby)
gPTP
gPTP
gPTP
gPTP
gPTP
gPTP
gPTP
gPTP
gPTP
gPTP
Clock slave
Principle:
▪ Independent back-up GM (hot standby) with
two independent timing domains
▪ Time synchronization over
redundant path
Notes
▪ No domain split when link failure
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
SUMMARY IEEE 802.1AS-REV RELIABILITY ENHANCEMENTS
Page 16
▪ IEEE 802.1AS:2011 is based on IEEE1588
▪ Redundancy can be achieved already using IEEE1588
− For automotive use-cases, tailoring is still required
− Interoperability could be issue
▪ IEEE 802.1AS-rev gives a standardized way to improve reliability of timing synchronization
▪ Redundant network paths can be used for time synchronization
▪ “Hot standby” grandmasters
▪ Improved diagnostic functions
▪ Tooling and industry support
▪ Interoperable
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
REDUNDANCY FOR LINK-BASED PROTOCOLSIEEE 802.1AS-REV + IEEE 802.1CB
Page 17
Clock master
gPTP
gPTP
Clock slave
gPTP
gPTP
gPTP
gPTP
Clock slave
Principle:
▪ Use 802.1CB for critical traffic and 802.1AS-rev
for time synchronization
Notes
▪ No interference
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
SUMMARY
Page 18
▪ We cannot rely on the network by default
▪ Redundancy does not come for free
▪ IEEE 802.1CB only for routable protocols
▪ For link-based protocols different solutions are required
▪ IEEE 802.1AS-rev has several reliability mechanisms available
▪ When using IEEE 802.1CB keep in mind that
▪ packets may arrive out of order
▪ packets may jitter when paths are switched
▪ Custom solutions are possible (and used)
▪ Infinite ways to solve the problem
TSN toolbox can help
No issue in mixing approaches
Interoperability risk
Reliability considerations required
© 2019 Renesas Electronics Corporation. All rights reserved. IEEE Ethernet & IP @ Automotive Technology Day
Detroit, September 2019
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