1. CSE-591: Term Project Self-stabilizing Network Algorithms by Tridib Mukherjee ASU ID : 993-76-1704

2. Self-stabilization Introduced by Dijkstra in 1974 Brings the system back to a valid state from any arbitrary initial state Used for tolerating intermittent and unpredictable transient faults Network Algorithms Token Rings Spanning Trees Network Resets

3. Top Level State Diagram Self-stabilization (Closure) Faults in the network Self- stabilization (Convergence) Invalid System State Valid System State System Start-up Self- stabilization (Convergence)

4. Diajkstra’s Definition Privilege Boolean predicate which is true in at least one process in the system Authorizes a process to make a move Action Legal system (global) state There must be at least one privilege in the system During an infinite time every process should be able to receive a privilege an infinite number of times

5. Network Algorithms Network Spanning Trees The basic network architecture for routing and token passing Broadcasting, Multicasting Operation A privileged action is executed if a fault occurs in a node Multicast trees for mobile ad-hoc networks Counter Flushing Used for network resets Can be used in token Rings or trees using PIF

6. Valid Spanning Tree 0 12 87 5346 Level 1 Level 2 Level 3 Level 4 Root Node (Source Node) Leaf Nodes (Group Members)

7. Invalid Spanning Tree 0 12 87 5346 Root Node (Source Node) Leaf Nodes (Group Members)

8. First Step of Stabilization 0 12 87 5346 Root Node (Source Node) Leaf Nodes (Group Members) Level 1

9. Subsequent Stabilization Step (Constitutes the valid tree in this case) 0 12 87 5346 Root Node (Source Node) Leaf Nodes (Group Members) Level 1 Level 2 Level 3 Level 4

10. Practical Issues Stabilization Time Can be reduced by proper scheduling Optimized by the use of Fault-containment Contains the effect of faults Scheduling is implicit Service Unavailable during the time of stabilization Increases end-to-end latency for the network service Effects of faults are unnecessarily propagated through the network Mobile Ad hoc networks & Sensor Networks Energy Efficiency Periodic information exchange can expensive

11. Questions??