Lab Part. Bernhard Frömel /34. Institut für Technische Informatik Technische Universität Wien Deterministic Networking VU SS14

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1 1/34 Bernhard Institut für Technische Informatik Technische Universität Wien VU SS

2 2/34 Motivation Emergence Self- Organization E versus SO Part I Emergence and Self-Organization

3 3/34 Fireflies synchronize Motivation Emergence Self- Organization E versus SO

4 Fireflies synchronize We understand them 1! Motivation Emergence Self- Organization E versus SO F07/NetLogo/Firefly.html 4/34

5 Flocking birds Motivation Emergence Self- Organization E versus SO Emergent behavior in flocks [1] 5/34

6 Internet Motivation Emergence Self- Organization E versus SO World Wide Web: number of links high for few pages, low for most pages 2 TCP based flows synchronize at network bottle necks, simultaneous inc-/decrease of throughput 2 6/34

7 7/34 Emergent Phenomena Motivation Emergence Self- Organization E versus SO No generally accepted definition of emergence strong versus weak emergence show up as a surprise (subjectively perceived properties useful?) open research Sensible definition: Emergence: A phenomenon of a whole at the macro-level is emergent if and only if it is new with respect to the non-relational phenomena of any of its proper parts at the micro-level. AMADEOS, Conceptual Model

8 8/34 Motivation Emergence Self- Organization E versus SO Characteristics of Emergence [2] Emergent properties are: Origin: Interacting Parts: Parts need to interact, parallelism is not enough Decentralized Control: only local mechanisms are used to influence global behavior Coherence: logical and consistent correlation of parts at micro-level persistent pattern regardless of added/removed parts Micro-Macro effect: effect that comes into existence at macro level (also called emergent) by interaction of parts at the microlevel Two-Way Link: emergent has causal effect on behavior of parts at micro-level Radical Novelty: emergent not explicitly defined Non-linear behavior of parts Feedback/Feedforward mechanisms Time delays

9 9/34 Self-Organization Motivation Emergence Self- Organization E versus SO Working definition: Self-Organisation is a dynamical and adaptive process where systems acquire and maintain structure themselves, without external control. [2] Properties of Self-Organization: Autonomy: absence of external control Increase in Order: convergence to confined set in state space Adaptability/Robustness: convergence robust w.r.t. perturbation and changes

10 10/34 Emergence (E) versus Self-Organization (SO) Motivation Emergence Self- Organization E versus SO Not synonyms! Both are dynamic processes arising over time E robust w.r.t. entering/leaving parts at micro-level SO robust w.r.t. changes of input and maintaining increased order One without the other possible (see [2]) In combination able to structure complex systems by keeping constituent parts simple Linking E and SO, different viewpoints: SO causes E: interaction of parts are SO, SO situated at micro-level SO effect of E: emergents become more organized, SO is a property of E

11 11/34 Clock Sync System Model Protocol Part II Distributed Clock Synchronization

12 12/34 Self-Stabilizing Distributed Clock Synchronization [3] Clock Sync System Model Protocol Problem: synchronize all local clocks up to precision π achieve and maintain precision π across all independent local clocks by exchange of messages no central control unknown initial conditions (i.e., local clock values arbitrary) How to do that?

13 12/34 Self-Stabilizing Distributed Clock Synchronization [3] Clock Sync System Model Protocol Problem: synchronize all local clocks up to precision π achieve and maintain precision π across all independent local clocks by exchange of messages no central control unknown initial conditions (i.e., local clock values arbitrary) How to do that? Solution: Emergence + Self-Organization Execute a protocol locally to achieve desired global effect Without external control input

14 13/34 Asynchronous Distributed System Model Clock Sync System Model Protocol Nodes (processors) contain local oscillators with bounded drift rate ρ, arbitrary phase Local oscillator generates clock ticks that are counted by discrete LocalTimer Nodes interconnected by directed channels according to topology (strongly connected, no self-loops, no multi-edges) Source node broadcasts messages to all directly connected destination nodes Delivery order of messages arbitrary No-fault assumption: all nodes execute protocol correctly, all communication channels transport messages reliably according to specified parameters

15 14/34 Clock Sync System Model Protocol Drift Rate Bound ρ and Relative Drift δ(t) Drift of an oscillator is the frequency ratio of that oscillator and a reference oscillator oscillating perfectly aligned to real-time Drift rate is drift osc 1 Assumption: oscillators have a known bounded drift rate ρ: 0 < ρ << 1 Maximum drift of fastest LocalTimer (discrete) over a time duration t is: (1 + ρ)t Maximum drift of slowest LocalTimer: (1 + ρ) 1 t Maximum relative drift δ(t): δ(t) = ((1 + ρ) (1 + ρ) 1 )t.

16 15/34 Clock Sync System Model Communication Delays Communication delay D, bounded: D 1 Network imprecision d, bounded: d 0 Communication latency γ: γ = (D + d). Protocol Figure : Event-Response Delay and Network Impression [3]

17 16/34 Protocol Description Clock Sync System Model Protocol System has two states: synchronized: all nodes are within precision π unsynchronized: during start-up, dynamic changes of nodes Synchronization protocol executed at each node transitions system to synchronized state (convergence) Synchronization protocol must be repeatedly reexecuted to maintain synchronized state (closure, stability) Nodes communicate by exchange of Sync messages Node times-out in case it s LocalTimer reaches max. value P (resynchronization period), LocalTimer resets

18 17/34 Protocol Execution Clock Sync System Model Protocol Node restarts resynchronization process if LocalTimer times-out, or a Sync message is received Time-out broadcast Sync message Received Sync message: reset LocalTimer and relay Sync message Eventually all nodes participate in (re)synchronization process Prevent cascading effects: Ignore temporally close Sync messages following a Sync message (ignore window)

19 18/34 Clock Sync Protocol in Pseudocode Executed each time step: System Model Protocol

20 19/34 TTEthernet Development Cluster TTEthernet Simulation Tools Part III Lab Environment

21 Development Environment TTEthernet Development Cluster TTEthernet Simulation Tools Gbit/s TTEthernet Development System Four nodes (x86, Ubuntu LTS, ), redundant TTEthernet switch setup Available Demo application showing video&audio streaming (best-effort vs time-triggered) login: demonstrator / demo26 don t update the whole distributions (installing additional software via sudo apt-get install should be safe (in most cases (probably))) work on Video Client 4 All TTEthernet Tool DVDs/CDs: ~/Desktop/tte_cds 20/34

22 21/34 Building TTEthernet Applications [5] TTEthernet Development Cluster TTEthernet Simulation Tools Define network configuration Implement application code Create the schedule (TTE Demo Scheduler) *.xml Compile applications Create device configurations (TTE Build) *.hex Load switches (TTE Load) Start applications

23 22/34 Building/Changing the Schedule TTEthernet Development Cluster TTEthernet Simulation Tools???

24 23/34 TTEthernet Development Cluster TTEthernet Simulation Tools Omnet++, INET, and CoRE4INET [4] Omnet++ is an open-source network simulation framework to build simulators wired, wireless, on-chip, queueing networks,... Eclipse based IDE graphical visualization of simulation INET framework: an open-source communication networks simulation package support for: UDP, TCP, IPv4, IPv6, Ethernet, , 802.1e (QoS extension), (WiMAX),... CoRE4INET: extension of INET for real-time Ethernet TTEthernet (SAE AS6802), Time-Sensitive (TSN), formerly known as: IEEE Audio Video Bridging (AVB)) host-, switch-, and clock models host contains implementation of TTEthernet-API

25 24/34 CoRE4INET, INET Integration [4] TTEthernet Development Cluster TTEthernet Simulation Tools

26 25/34 CoRE4INET, In Action TTEthernet Development Cluster TTEthernet Simulation Tools

27 26/34 Tasks Logistics and Grading Part IV Assignment

28 27/34 Tasks Logistics and Grading Tasks 1. Implement a distributed clock synchronization protocol Based on the paper: A Self-Stabilizing Distributed Clock Synchronization Protocol for Arbitrary Digraphs, Mahyar R. Malekpour Use (real) TTEthernet for simple four nodes topology Use simulation framework for simulating hundreds of nodes in different topologies (Schedule?) 2. Compare achieved clock precision π over time on conventional Ethernet and TTEthernet (or other Time-Triggered Ethernets in simulation) Under different (self-chosen) network load/fault scenarios Conduct measurements, use TTEthernet global clock 3. Discuss results Hint : The best-effort (traffic class) solution of the group from last year is available in the lab environment.

29 28/34 Deliverables Tasks Logistics and Grading Implementation Documentation/Lab report English Include rudimentary HowTo develope TTEthernet applications (tool usage + schedules) Focus on concise presentation of the implementation and discussion of results

30 29/34 Logistics and Grading Tasks Logistics and Grading Start: now Finish: September (latest) Work in groups, group size depends on number of participants Location: Institute Lab Fallstudienlabor Offer: weekly meetings Grading Deliverables: 75 points Delivery Talk/Presentation of results: 25 points

31 30/34 Summary Q&A Credits References Part V End

32 31/34 Summary Summary Q&A Credits References Emergence and self-organization Self-Stabilizing distributed clock synchronization Available lab equipment and environment Assignment

33 32/34 Questions & Answers Summary Q&A Credits References

34 33/34 Summary Q&A Credits References Credits Images: https: // files/styles/lightbox/public/field/image/ SynchClock.jpg?itok=DEFoWZod

35 Summary Q&A Credits References References [1] Felipe Cucker and Steve Smale. Emergent behavior in flocks. Automatic Control, IEEE Transactions on, 52(5): , [2] Tom De Wolf and Tom Holvoet. Emergence versus self-organisation: Different concepts but promising when combined. In Engineering self-organising systems, pages Springer, [3] Mahyar R Malekpour. A self-stabilizing distributed clock synchronization protocol for arbitrary digraphs. National Aeronautics and Space Administration, Langley Research Center, [4] Till Steinbach, Hermand Dieumo Kenfack, Franz Korf, and Thomas C. Schmidt. An Extension of the OMNeT++ INET Framework for Simulating Real-time Ethernet with High Accuracy. In SIMUTools th International OMNeT++ Workshop, pages , New York, USA, March ACM DL. [5] TTTech. TTEthernet Introduction Workshop, Slides. TTTech Computertechnik AG, /34