Deterministic Networking Lab Part...I TTEthernet (SAE AS6802), Time-Sensitive Networking (TSN),...

DeterministicNetworkingLab Part

Frömel

Deterministic NetworkingLab Part

Bernhard Frömel

Institut für Technische InformatikTechnische Universität Wien

-182.730 Deterministic Networking VU

SS14

23. 05. 2014

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Frömel

Motivation

Emergence

Self-Organization

E versus SO

Part I

Emergence and Self-Organization

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Motivation

Emergence

Self-Organization

E versus SO

Fireflies synchronize

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Motivation

Emergence

Self-Organization

E versus SO

Fireflies synchronizeWe ”understand” them1!

1http://web.eecs.utk.edu/~mclennan/Classes/420-594-F07/NetLogo/Firefly.html

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http://web.eecs.utk.edu/~mclennan/Classes/420-594-F07/NetLogo/Firefly.html

http://web.eecs.utk.edu/~mclennan/Classes/420-594-F07/NetLogo/Firefly.html


Frömel

Motivation

Emergence

Self-Organization

E versus SO

Flocking birds

I www.lalena.com/AI/Flock/Flock.aspxI ”Emergent behavior in flocks” [1]

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www.lalena.com/AI/Flock/Flock.aspx


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Motivation

Emergence

Self-Organization

E versus SO

Internet

I World Wide Web: number of links high for few pages, lowfor most pages2

I TCP based flows synchronize at network bottle necks,simultaneous inc-/decrease of throughput

2http://internet-map.net/6/34

http://internet-map.net/


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Motivation

Emergence

Self-Organization

E versus SO

Emergent Phenomena

I No generally accepted definition of emergenceI strong versus weak emergenceI show up as a surprise (subjectively perceived properties

useful?)I ⇒ open research

I ’Sensible’ definition:”Emergence: A phenomenon of a whole at themacro-level is emergent if and only if it is newwith respect to the non-relational phenomena ofany of its proper parts at the micro-level.”AMADEOS, Conceptual Model

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Motivation

Emergence

Self-Organization

E versus SO

Characteristics of Emergence [2]I Emergent properties are:

I Interacting Parts: Parts need to interact, parallelism is notenough

I Decentralized Control: only local mechanisms are used toinfluence global behavior

I Coherence: logical and consistent correlation of parts atmicro-level⇒ persistent pattern regardless ofadded/removed parts

I Micro-Macro effect: effect that comes into existence atmacro level (also called emergent) by interaction of partsat the microlevel

I Two-Way Link: emergent has causal effect on behavior ofparts at micro-level

I Radical Novelty: emergent not explicitly defined

I Origin:I Non-linear behavior of partsI Feedback/Feedforward mechanismsI Time delays

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Motivation

Emergence

Self-Organization

E versus SO

Self-Organization

I Working definition:

”Self-Organisation is a dynamical and adaptiveprocess where systems acquire and maintainstructure themselves, without externalcontrol.” [2]

I Properties of Self-Organization:I Autonomy: absence of external controlI Increase in Order: convergence to confined set in state

spaceI Adaptability/Robustness: convergence robust w.r.t.

perturbation and changes

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Motivation

Emergence

Self-Organization

E versus SO

Emergence (E) versus Self-Organization (SO)

I Not synonyms!

I Both are dynamic processes arising over time

I E robust w.r.t. entering/leaving parts at micro-level

I SO robust w.r.t. changes of input and maintainingincreased order

I One without the other possible (see [2])

I In combination able to structure complex systems bykeeping constituent parts simple

I Linking E and SO, different viewpoints:I SO causes E: interaction of parts are SO, SO situated at

micro-levelI SO effect of E: emergents become more organized, SO is a

property of E

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Clock Sync

SystemModel

Protocol

Part II

Distributed Clock Synchronization

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Clock Sync

SystemModel

Protocol

Self-Stabilizing Distributed Clock Synchronization [3]

I Problem: synchronize all local clocks up to precision πI achieve and maintain precision π across all independent

local clocks by exchange of messagesI no central controlI unknown initial conditions (i.e., local clock values arbitrary)

I How to do that?

I Solution: Emergence + Self-OrganizationI Execute a protocol locally to achieve desired global effectI Without external control input

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Clock Sync

SystemModel

Protocol

Self-Stabilizing Distributed Clock Synchronization [3]

I Problem: synchronize all local clocks up to precision πI achieve and maintain precision π across all independent

local clocks by exchange of messagesI no central controlI unknown initial conditions (i.e., local clock values arbitrary)

I How to do that?I Solution: Emergence + Self-Organization

I Execute a protocol locally to achieve desired global effectI Without external control input

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Clock Sync

SystemModel

Protocol

Asynchronous Distributed System Model

I Nodes (processors) contain local oscillators with boundeddrift rate ρ, arbitrary phase

I Local oscillator generates clock ticks that are counted bydiscrete LocalTimer

I Nodes interconnected by directed channels according totopology (strongly connected, no self-loops, nomulti-edges)

I Source node broadcasts messages to all directlyconnected destination nodes

I Delivery order of messages arbitrary

I No-fault assumption: all nodes execute protocol correctly,all communication channels transport messages reliablyaccording to specified parameters

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Clock Sync

SystemModel

Protocol

Drift Rate Bound ρ and Relative Drift δ(t)I Drift of an oscillator is the frequency ratio of that oscillator

and a reference oscillator oscillating perfectly aligned toreal-time

I Drift rate is|driftosc − 1|

I Assumption: oscillators have a known bounded drift rate ρ:

0 < ρ << 1

I Maximum drift of fastest LocalTimer (discrete) over a timeduration t is:

(1 + ρ)t

I Maximum drift of slowest LocalTimer:

(1 + ρ)−1t

I Maximum relative drift δ(t):

δ(t) = ((1 + ρ)− (1 + ρ)−1)t.

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Clock Sync

SystemModel

Protocol

Communication DelaysI Communication delay D, bounded: D ≥ 1I Network imprecision d, bounded: d ≥ 0I Communication latency γ:

γ = (D + d).

Figure : Event-Response Delay and Network Impression [3]

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Clock Sync

SystemModel

Protocol

Protocol Description

I System has two states:I synchronized: all nodes are within precision πI unsynchronized: during start-up, dynamic changes of

nodes

I Synchronization protocol executed at each nodetransitions system to synchronized state (convergence)

I Synchronization protocol must be repeatedly reexecutedto maintain synchronized state (closure, stability)

I Nodes communicate by exchange of Sync messages

I Node times-out in case it’s LocalTimer reaches max. valueP (resynchronization period), LocalTimer resets

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Clock Sync

SystemModel

Protocol

Protocol Execution

I Node restarts resynchronization process ifI LocalTimer times-out, orI a Sync message is received

I Time-out⇒ broadcast Sync message

I Received Sync message:⇒ reset LocalTimer and relaySync message

I Eventually all nodes participate in (re)synchronizationprocess

I Prevent cascading effects: Ignore temporally close Syncmessages following a Sync message (ignore window)

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Clock Sync

SystemModel

Protocol

Protocol in Pseudocode

Executed each time step:

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TTEthernetDevelop-mentCluster

TTEthernet

SimulationTools

Part III

Lab Environment

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TTEthernet

SimulationTools

Development Environment

I Gbit/s TTEthernet Development SystemI Four nodes (x86, Ubuntu 10.04 LTS, 2.6.32), redundant

TTEthernet switch setupI Available Demo application showing video&audio

streaming (best-effort vs time-triggered)I login: demonstrator / demo26I don’t update the whole distributions (installing additional

software via sudo apt-get install should be safe(in most cases (probably)))

I work on ’Video Client 4’I All TTEthernet Tool DVDs/CDs: ~/Desktop/tte_cds

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TTEthernet

SimulationTools

Building TTEthernet Applications [5]

I Define network configuration

I Implement application code

I Create the schedule (TTE Demo Scheduler)⇒ *.xml

I Compile applications

I Create device configurations (TTE Build)⇒ *.hex

I Load switches (TTE Load)

I Start applications

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TTEthernet

SimulationTools

Building/Changing the Schedule

???

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TTEthernet

SimulationTools

Omnet++, INET, and CoRE4INET [4]

I Omnet++ is an open-source network simulation frameworkto build simulators

I wired, wireless, on-chip, queueing networks, ...I Eclipse based IDEI graphical visualization of simulation

I INET framework: an open-source communication networkssimulation package

I support for: UDP, TCP, IPv4, IPv6, Ethernet, 802.11, 802.1e(QoS extension), 802.16 (WiMAX), . . .

I CoRE4INET: extension of INET for real-time EthernetI TTEthernet (SAE AS6802), Time-Sensitive Networking

(TSN), formerly known as: IEEE 802.1 Audio Video Bridging(AVB))

I host-, switch-, and clock modelsI host contains implementation of TTEthernet-API

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TTEthernet

SimulationTools

CoRE4INET, INET Integration [4]

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TTEthernet

SimulationTools

CoRE4INET, In Action

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Tasks

Logisticsand Grading Part IV

Assignment

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Tasks

Logisticsand Grading

Tasks

1. Implement a distributed clock synchronization protocolI Based on the paper:

”A Self-Stabilizing Distributed Clock SynchronizationProtocol for Arbitrary Digraphs”, Mahyar R. Malekpour

I Use (real) TTEthernet for simple four nodes topologyI Use simulation framework for simulating hundreds of

nodes in different topologies (Schedule?)

2. Compare achieved clock precision π over time onconventional Ethernet and TTEthernet (or otherTime-Triggered Ethernets in simulation)

I Under different (self-chosen) network load/fault scenariosI Conduct measurements, use TTEthernet global clock

3. Discuss results

’Hint’: The best-effort (traffic class) ’solution’ of the group fromlast year is available in the lab environment.

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Tasks


Deliverables

I ImplementationI Documentation/Lab report

I EnglishI Include rudimentary HowTo develope TTEthernet

applications (tool usage + schedules)I Focus on concise presentation of the implementation and

discussion of results

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Tasks


Logistics and Grading

I Start: now

I Finish: September (latest)

I Work in groups, group size depends on number ofparticipants

I Location: Institute Lab ‘Fallstudienlabor’

I Offer: weekly meetingsI Grading

I Deliverables: 75 pointsI Delivery Talk/Presentation of results: 25 points

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Summary

Q&A

Credits

References

Part V

End

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Summary

Q&A

Credits

References

Summary

I Emergence and self-organization

I Self-Stabilizing distributed clock synchronization

I Available lab equipment and environment

I Assignment

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Summary

Q&A

Credits

References

Questions & Answers

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Summary

Q&A

Credits

References

CreditsI Images:

I https://www.flickr.com/photos/jamesjordan/I https://www.flickr.com/photos/87310153@N07/I https:

//www.flickr.com/photos/richardsmith155/I https://www.flickr.com/photos/53297845@N06/I http://www.automationworld.com/sites/default/

files/styles/lightbox/public/field/image/

SynchClock.jpg?itok=DEFoWZod

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https://www.flickr.com/photos/jamesjordan/

https://www.flickr.com/photos/87310153@N07/

https://www.flickr.com/photos/richardsmith155/

https://www.flickr.com/photos/richardsmith155/

https://www.flickr.com/photos/53297845@N06/

http://www.automationworld.com/sites/default/files/styles/lightbox/public/field/image/SynchClock.jpg?itok=DEFoWZod




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Summary

Q&A

Credits

References

References[1] Felipe Cucker and Steve Smale.

Emergent behavior in flocks.Automatic Control, IEEE Transactions on, 52(5):852–862,2007.

[2] Tom De Wolf and Tom Holvoet.Emergence versus self-organisation: Different concepts butpromising when combined.In Engineering self-organising systems, pages 1–15.Springer, 2005.

[3] Mahyar R Malekpour.A self-stabilizing distributed clock synchronization protocolfor arbitrary digraphs.National Aeronautics and Space Administration, LangleyResearch Center, 2011.

[4] Till Steinbach, Hermand Dieumo Kenfack, Franz Korf, andThomas C. Schmidt.An Extension of the OMNeT++ INET Framework forSimulating Real-time Ethernet with High Accuracy.In SIMUTools 2011 – 4th International OMNeT++ Workshop,pages 375–382, New York, USA, March 21-25 2011. ACMDL.

[5] TTTech.TTEthernet Introduction Workshop, Slides.TTTech Computertechnik AG, 2013.

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Deterministic Networking Lab Part...I TTEthernet (SAE AS6802), Time-Sensitive Networking (TSN),...

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