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Nicolas NAVET, University of Luxembourg
2017 IEEE Standards Association (IEEE-SA) Ethernet & IP @ Automotive Technology Day
31 October - 2 November 2017, 2017 | San Jose, CA, USA
Josetxo VILLANUEVA, Groupe RenaultJörn MIGGE, RealTime-at-Work (RTaW)Marc BOYER, Onera
Insights on the performance and configuration of AVB and TSN in
automotive applications
Use-cases for Ethernet in vehicles
2
Infotainment
• Synchronous traffic
• Mixedaudio andvideo data
• MOSTlike
Cameras
• Highdata rates
• Continuous streaming
• Canbe used by ADAS
Diag.&flashing
• Interfacing toexternal tools
• Highthroughputneeded
Control functionsADAS
• Time-sensitivecommunication
• Smalland largedata payload
• CoverCAN/Flexray use cases
1TWISTED-PAIRe.g.,sub-10mslatencyconstraints
Bandwidthguarantees:e.g.10Mbit/se.g.10-30mslatencyconstraintsperimage(e.g.42frames)
Renault Ethernet prototype network
3
4Cameras30and60fps 3ControlUnits
4Displays 3domainMasters
1Gbit/s
27%↙
↗60%
←24%
↖46%
↑43%
↗35%
↗59%
50%↙
→49%
←23%
#Nodes 14#Switches 5#streams 41
Workloadperlink
Min:<1%,med:11%max:60%
Linkdatarates 100Mbit/sand1Gbit/s(1link)
Types of traffic
4
Command&Control(CC)
Audiostreams
VideoStreams
File&datatransfer,diag.
ü 11streams,256to1024byteframesü uptosub-10msperiodanddeadlineüdeadlineconstraints(hard)
ü 8streamsü 128and256byteframesüuptosub-10msperiodanddeadlineü deadlineconstraints(soft)
ü 2ADAS+6Visionstreams,upto30*1446byteframeeach16msü10ms or30ms deadlineü hardandsoftdeadlineconstraints
ü14streams,TFTPtrafficpatternü Upto0.2msperiodüBandwidthguarantee:upto20Mbits
QoS protocols on top of Ethernet
Streamscanbeassignedto8prioritylevels
Benefits:üStandardandsimpleüefficientatthehighestprioritylevels
Limitations:ü Notfine-grainedenoughtoaccommodateallkindsofrequirements
IEEE802.1QAudio Video
Bridging (AVB)Time-Sensitive
Networking (TSN)
5
TemporalQoS=managinginterferingtrafficPriority-based TrafficShaping Time-triggered(TT)
Credit-BasedShaper(CBS)and6prioritylevelsbelow
Benefits:üBasedonanexistingstandardüPerformanceguaranteeforAVBüNostarvationforbest-efforttraffic
Limitations:üNotsuitedforcontroltraffic
Time-AwareShaper(TAS)enablesTTtransmissions
Benefits:ü Strongtimeconstraintscanbemet(iftaskschedulingistailoredtocommunication)üCanbecombinedwithAVB
Limitations:üQuitecomplexandhardtoconfigureüRelyonasynchronizationprotocol
Support in the switches
6
TrafficShaping
TASQueue
Priority-basedscheduling
Time-Triggeredtransmission
BestEffortQueues
Upto8priorityleveloverall [FigurefromAshjaei2017]
Under IEEE802.1Q – 3rd hop
7
High-prioritystreams
Best-effortstreams
Under AVB/CBS – 3rd hop
High-prioritystreams
Best-effortstreams
AVBSR-A
Best-effortframesgetthechancetobetransmittedsooner
Obtainedbysimulation
inRTaW-Pegase
TSN/TAS: coordinating gate scheduling tables
8
Sendingnode
Switch#1
Switch#2
Whitebands=transmissionallowed|greybands=notallowed
Solutions experimented
9
SeveralmechanismstoensureQoS w.r.t.timing,butwhicharethemostefficientforautomotivesystems?
TSNAVBIEEE802.1Q
StandardAVBclasseswithC&Casbest-effort
AVB“Custom-Classes”withC&Casbest-effort
IEEE802.1Qwithandwithout“pre-shaping”
AVB“Custom-Classes”withC&CunderTSN/TAS
TSN/TAStoemulateAVBtoshapeaudio/videostreamsNotdiscussedhere- seeTSN/A2017
#1
#2
#3
#4
C&C=Command&Control
#5
Verification techniques
10
Prob
ability
Responsetime
Simulationmax.
Upper-boundwithschedulabilityanalysis
Q5Q4
(actual)worst-casetraversaltime(WCTT)
Easilyobservableevents InfrequenteventsTestbed &Simulation
LongSimulation
Schedulabilityanalysis
Used inthis study
ü Longsimulationhere=48hoursofdrivingà 350000transmissionsfor500msframesü Metrics:communicationlatencies,bandwidthusageandbufferoccupancies
ToolsetüRTaW-Pegase – modeling/analysis/configurationofswitchedEthernet(automotive,avionics)+CAN(FD)+taskscheduling
üHigher-levelprotocols(e.g.SomeIP)andfunctionalbehaviorcanbeprogrammedinCPAL® language[4]üDevelopedsince2009inpartnershipwithOneraüEthernetusersincludeDaimlerCars,AirbusHelicopters,CNESandABB
üWorst-caseTraversalTime(WCTT)analysis- basedonNetwork-Calculus,corealgorithmsarepublishedandprovencorrect
üTiming-accurateSimulation – ps resolution,≈4×106 events/seconasinglecore(I7- 3.4Ghz),suitedupto(1-106)quantiles
üLower-boundsontheWCTT: “unfavorablescenario”+Benchmarking:“NetAirbench” 11
Evaluationtechniques
Case-study – sol. #1 and #2standard AVB and AVB custom classes
12
Default traffic priorities for AVB solution
13
Command&Control(C&C)
Audiostreams
Non-ADASVideoStreams
File&datatransfer,diag.
ToppriorityAVBSR-A
SecondprioritylevelAVBSR-B
Best-effortLowestpriority
Best-effortHighestpriority
Decreasingpriorities
Feasiblesolution?
ADASVideoStreams
Automotive AVB SR Class and performance guarantees
14
[AVNUAutomotiveProfile]
Over7hops
[AVNUAutomotiveProfile]
Sol #1 - standard AVB
15
VS
SR-A:emissionspreadover8ms=10ms- 2ms⇒ 64framesof703bytes,oneevery125us
ü Let’sconsiderADASvideostreamUC3610Mbit/s@30FPS- deadlinetoreceiveanimageis10ms
8ms
Image130frames
Image430frames
Image230frames
Image330frames Nativeformat:
30x1400bytesframesevery33ms
Alsoworst-caseanalysiscouldnotprovideboundsbecauseofoverallpeak-load>100%.
StandardAVBdoesnotprovideasolution!üOverheadofusingsmallerframes– peakloadover8msis46%forUC36ü2suchADASVideostreamsonalink⇒ AVBloadrequirementsof75%notmet⇒ 2msguaranteedoesnothold
2ms
Sol #1 - standard AVBRelaxing image deadline to 15ms instead of 10ms
for the 2 ADAS video streams
16
AVBsolution:SR-Awith104framesof450bytes,oneevery125us⇒ 13ms+communicationlatency<2ms
13ms
104framesof450bytes
Worst-caseresponsetimeanalysisneededsinceAVBloadconditiondoesnothold
Sol #2 – a feasible solution with AVB “custom classes”
17
ü CustomClass=non-125/250usCMI⇒ noAVBguaranteesthusworst-caseanalysisneededü Sendvideoin“nativeformat”=30framesof1400bytespayloadevery33.3ms⇒ noadditional“repackaging”overhead
ü CustomIdleslopes:minimalIdleSlopesalongthepathallowingtojustmeetAVBtraffictimingconstraints:⇒ TightIdle-Slope algorithminRTaW-Pegase
àWecanpushthelimitsofAVBwith“smart”configurationtools
Customclassesoffersasolution
- Goal#1:ADASvideostreamsunderAVBandC&Ctrafficmeetsdeadlines
- Goal#2:Reducedworst-caselatenciesforbest-effortstreams
- Goal#3:Throughputrequirementsforspecificbest-effortstreamsmet
ü
Goal #2: Worst-case latencies for best-effort streams
18
IEEE802.1QAVBTightIdle-SlopeAVBMinimalIdle-Slope*
UsingAVBwithTightIdle-SlopealgorithminsteadofIEEE802.1Qimprovesworst-caselatencies forbest-
effortstreamsby73%onaverage– upto87%
Worst-caselatencies(ms)
Best-effortstreamsonly*Videostreamsaremissingdeadlines
Goal #3: Bandwidth availability for specific streams
19
ü Perf.requirementsmaynotbelatenciesbutbandwidthusage,e.g.10Mbit/sforFileTransferstreamà averagelatenciestellifobjectivesaremet
IEEE802.1QAVBTightIdle-SlopeAVBMinimalIdle-Slope*
UsingAVBwithTightIdle-SlopealgorithminsteadofIEEE802.1Qimprovesaveragelatencies forbest-effortstreamsby54%onaverage– upto86%
ex:TFTPstreamUC30meets10Mbit/sobj.asbothrequestandresponseavg latenciesarebelow0.4ms– notmetunderIEEE802.1Q
Best-effortstreamsonly
Averagelatencies(ms)
*Videostreamsaremissingdeadlines
Case-study – sol. #3using IEEE802.1Q with pre-shaping
20
Case-study: priorities for IEEE802.1Q solution
21
Command&Control(C&C)
AudioStreams
File&datatransfer,diag.
Toppriority
Secondprioritylevel
Best-effort
Thirdprioritylevel
Decreasingpriorities
VideoStreams
IEEE802.1Q with pre-shaping
22
ü Pre-shaping=inserting“well-chosen”minimumdistancebetweenframesofaburstonthesendersideonly- othercharacteristicsoftrafficunchanged
ü Pre-shapingappliedtoVideostreams
Findingappropriatevaluesisnotstraightforward..
IEEE802.1Q with pre-shaping for VideoAverage latencies for best-effort streams
23
IEEE802.1QIEEE802.1Qwithpre-shapingAVBTightIdle-Slope
Pre-shapingunderIEEE802.1Qimprovesaveragelatencies forbest-effortstreamsby
54%onaverage– upto86%– similarperformanceasusingAVBcustomclasses
Best-effortstreamsonly
DeadlinesofC&C,Video,Audiomet– likewithoutPre-shaping
Averagelatencies(ms)
IEEE802.1Q with pre-shaping for Video Worst-case latencies for best-effort streams
24
IEEE802.1QIEEE802.1Qwithpre-shapingAVBTightIdle-Slope
Pre-shapingunderIEEE802.1Qimprovesworst-caselatencies forbest-effortstreamsby66%onaverage– upto90%- similarperformanceasusingAVBcustomclasses
Worst-caselatencies(ms)
Best-effortstreamsonly
Case-study – sol. #4using TSN/TAS to reduce C&C latencies
25
Case-study: priorities for TAS/CBS solution
26
Command&Control(C&C)
AudioStreams
File&datatransfer,diag.
TopprioritylevelUnderAVB/CBS
Best-effort
Decreasingpriorities
VideoStreams
ThirdprioritylevelWithTASconfiguredtominimizeC&Clatencies
SecondprioritylevelUnderAVB/CBS
ConfigurationofAVB/CBSusingcustom
classeswithtightIdle-Slope
algorithm
C&CisolatedthroughTAS
Improvements brought by TSN/TAS for Command & Control traffic
ü AllC&CstreamsunderTAS– taskandframesaresynchronizedü GateschedulingconfigurationdonewithASAP algorithminRTaW-Pegase thataimstominimize
latenciesforTAStraffic(i.e.,notrade-off)
27
WithIEEE802.1QwithC&CattoppriorityAVBTightIdle-SlopewithTSN/TASAVBTightIdle-Slope=sol.#2
Maxim
umlatencies(ms)
UsingTSN/TASforC&CtrafficwithASAPalgorithmimprovesmaximumlatencies forC&Cstreams
by54%onaverageoverIEEE802.1Qby60%overAVBwithoutTAS
C&Cstreamsonly
TSN/TAS for C&C traffic + AVB/CBS for audio/videoü MaxlatenciesofAudio/Video/Best-effortalmostunaffectedbyTAS(<3%onavg)ü Alldeadlinesandbandwidthavailabilityconstraintsmet.
IEEE802.1Qwithoutpre-shapingAVBTightIdle-SlopewithTSN/TASAVBTightIdle-Slope
ADASVideostreamswith10msdeadlines
Videostreamswith30msdeadlines
Maxim
umlatencies(ms)
Allstreams
Bestoverall resultsTAS+CBSallow fine-tuning theQoSprovided toeach classoftraffic
28
Conclusion and a look forward
29
Solutions experimented & results achieved
IEEE802.1Qwithoutpre-shaping
IEEE802.1Qwithpre-shaping
AVBstandardclasses
AVBcustomclasses
TSN/TASforvideowithoutAVB/CBS
TSN/TASwithAVB/CBSü
û
û
ü
üû
Fine-grainedconfigurationofprotocolsparametersrequiredtoobtainall3feasiblesolutions– no“one-fits-all”solutionwrt parameters
Throughputrequirementsforbest-effortnotmet
10msforADASvideonotmet
Bandwidth forbest-effortnotmet
30
1
Insight from the case-study
31
2
3
Mixed-criticalitytrafficimpliesadiversityofcommunicationrequirementsinupcomingEthernet
networks:deadlines(soft/hard),bandwidth,segmentedmessages,client-server,bufferusage,etc
IEEE802.1Qnotsuitedforbursty traffic(e.g.,video)withbest-efforttraffic:pre-shapingthebursty trafficbyinsertingidletimesprovidesimprovements
AVBcanbeananswertomanyneedsbutstandardclassesarenotenough
ü Scopeofapplicabilitytoonarrowevenforvideo-streams
ü pessimisticwrt timingguaranteesCustomclassesenablestogetthemostoutof
standardAVBcomponentbuttoolsmustbeusedforconfiguration&timingverification
4
Insight from the case-study
32
56
TSN/TASiseffectiveatimprovingthelatenciesforCommand&ControltrafficandcanalsobeusedtomimicAVB/CBSforstreamsbuttoolsmustbeused
forconfiguration&timingverification
Gigabit/sandframepreemptionmayhelptosimplifyprotocolstacksforsomeuse-cases
Configurationhasbecomeachallenge! priorities,AVBclasses,idleSlopes,TASgatescheduletable,
co-schedulingtask-messages,gatewayingstrategies,etcà impactonsafetyandcost-
effectiveness
Configurationandsystemsynthesis (e.g.,architecture)canandneedtobemuchfurther
automatedintheyearstocome!
