1. Sine-Wave Application v2.0 Pavel Čírtek

2. Sine-Wave Application v2.0 2 The Aim of the Work Create representative prototype of highly dependable synthetic application for TTP/C cluster Perform value-domain fault tolerance tests (every single fault should be tolerated)

3. Sine-Wave Application v2.0 3 Definitions TTP/C – Time triggered protocol (fulfils C class of safety requirements) TDMA – Time Divided Multiple Access TDMA round – every node has own time slot in one round

4. Sine-Wave Application v2.0 4 TTP/C node and cluster Communication Controller (CC) – executes TTP/C protocol Host Processor (HP) – executes application program Dual-port CNI (Computer Network Interface) memory – interconnection between CC and HP

5. Sine-Wave Application v2.0 5 Main goals Verify that a single fault (transient or permanent) can be tolerated Test resilience of app. output with regards to more complicated faults (attacking a single node) Test ability of TTP/C cluster to recover from more complicated faults (attacking more nodes)

6. Sine-Wave Application v2.0 6 Application work Get phase shift (S-node) Compute it through cluster (C-node) The result phase in A-node should be same as from S-node

7. Sine-Wave Application v2.0 7 Cluster Schema S-node – sensor C-node – computation A-node – actuator k – number of C-node pairs N – number of nodes = 2*k+4 m – “state memory”

8. Sine-Wave Application v2.0 8 Cluster timing Two TDMA rounds –Data frame (N-frame) –Initialization frame (I-frame) Tasks –TLF (lifesign) – right before sending (in every node) –Two computation tasks – somehow time shifted (in C-nodes)

9. Sine-Wave Application v2.0 9 Functionality of C-node Read data d i-1 from message Use data to recalculate state s i and new value d i –s i = f 1 (s i, d i-1 ) –d i = f 1 (s i, d i-1 ) Broadcast new value d i and s i Four values to compare (two nodes, TTP/C doubled bus)

10. Sine-Wave Application v2.0 10 Application data ROM (e.g. constants) Global data (stored in HP RAM memory) CNI data (special kind of global data, periodically updated by CC) Local data (initialized within every run of its task)

11. Sine-Wave Application v2.0 11 Fault injection Permanent fault – failed node is fail-silent (only two d i in next FTU) Transient faults: –Global data – four instances of result –Local data – two scenarios: does not influence the control flow only result (same as global data damaging) Influences the control flow – TTP/C should recognize it and restart HP

12. Sine-Wave Application v2.0 12 Conclusion The aim of model is to use fault injection to evaluate possibilities how to build safety-critical applications. Improvement of old version – node has its state