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CSE-591: Term Project. Self-stabilizing Network Algorithms by Tridib Mukherjee ASU ID : 993-76-1704. Self-stabilization. Introduced by Dijkstra in 1974 Brings the system back to a valid state from any arbitrary initial state
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CSE-591: Term Project Self-stabilizing Network Algorithms by Tridib Mukherjee ASU ID : 993-76-1704
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
Top Level State Diagram Self-stabilization (Closure) Faults in the network Valid System State Invalid System State Self-stabilization (Convergence) Self-stabilization (Convergence) System Start-up
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
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
Valid Spanning Tree Level 1 0 Level 2 1 2 Level 3 3 4 5 6 Level 4 7 8 Root Node (Source Node) Leaf Nodes (Group Members)
Invalid Spanning Tree 0 1 2 3 4 5 6 7 8 Root Node (Source Node) Leaf Nodes (Group Members)
First Step of Stabilization Level 1 0 1 2 3 4 5 6 7 8 Root Node (Source Node) Leaf Nodes (Group Members)
Subsequent Stabilization Step(Constitutes the valid tree in this case) Level 1 0 Level 2 1 2 Level 3 3 4 5 6 Level 4 7 8 Root Node (Source Node) Leaf Nodes (Group Members)
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