fault management in mobile ad-hoc networks by tridib mukherjee
TRANSCRIPT
Fault Management in Mobile Ad-Hoc Networks
by Tridib Mukherjee
Transient Faults in Mobile Ad-Hoc Networks
Mobility of the NodesError Prone MediumLink FailuresLow Battery PowerNode Corruption
Fault Tolerance
Ability of a system to perform its function correctly even in the presence of internal faults.
Makes the network system more dependable.
Hides the faults from the user.Two basic kinds of Fault Tolerance :
Proactive and Reactive.
Self Stabilization
Stabilizes a Distributed System to a legitimate state from any arbitrary initial state.
Used as a Proactive Fault Tolerant Scheme.
There are 2 properties : Closure and Convergence.
Self-stabilizing Multicast Routing Protocols For Mobile Ad-Hoc Networks
Shortest Path Spanning Tree (SPST)Used in this project
Maintains Shortest Path from source to destination.
Beacon Messages provide information about neighbors.
Recreates the tree in case of faults.Unnecessarily propagates limited faults
across the network.
Fault Containment
Contains the fault in the region where it has occurred
Improves stabilization time Considerably.Increases Computational and
Communication Overhead.Does not contain faults in all the desired
cases in Mobile Ad-Hoc Networks.Tradeoff needed for optimal Energy
Efficiency while managing the faults.
Fault-containment Algo.
can_stabilize :
Propose for Adaptation
Adapt to the changing Fault Scenarios.Use Self Stabilization where Fault
Containment can not contain the faults.Use Fault Containment where it can
contain the faults.
Fault Classification
Fault-Containable (FC) Faults Fault can be contained using Fault Containment
Non-Fault-Containable (NFC) Faults Fault Containment can not contain the faults Self-stabilization and Fault-containment have same
performance Fault-containment executes self-stabilization
internally Fault-containment adds computational overhead
Valid SPST Tree
R
A
X
M
Y
Level 0
Level 1
Level 2
Level 3
Level 4
M moves out
R
A
C
X
D
M
Y
Level 0
Level 1
Level 2
Level 3
Level 4
can_stabilize(Y) is falsecan_stabilize(X) is falsecan_stabilize(C) is falsecan_stabilize(D) is false
This is NFC fault
R
A
X
Y
Level 2
Level 3
Neighborhood of Y is different
R
A
C
X
D
M
Y
Level 0
Level 1
Level 2
Level 3
Level 4
can_stabilize(Y) is truecan_stabilize(A) is falsecan_stabilize(C) is falsecan_stabilize(D) is false
FC faults
The scenario of the previous slideFaults occurred due to corruption are FC
faultsBoth NFC and FC faults can occur in
multiple nodes simultaneouslyFor NFC faults, self stabilization is
executed internally
Two FC faults within 2 hops
R M
X
AY B
• Level of A gets corrupted to 6 • M moves out and X becomes the parent of Y • Both the FC faults become Non-containable • Distance of 2 hops is named as Containability Limit (CL)
0 1 2 3 4 5
Reason
Gp(Y) and Gp(A) are true
Can_stabilize(Y) and Can_stabilize(A) are false
So Fault Containing Algorithm executes self-stabilization internally
FC faults becomes NFC if they occur within CL
Improved_Can_Stabilize
Check if local action can nullify Gp in all the two hop neighbors instead of one hop neighbors as in the original algorithm
Otherwise check if local actions in all the one hop neighbors can eradicate fault in all the two hop neighbors
Improved Fault-containment
Reasoning
Gp(Y) and Gp(A) are true
Can_stabilize(Y) and Can_stabilize(A) are also true
Fault Containing Algorithm executes self-stabilization internally only if faults are NFC
Containability Limit is 0
Simulation
Simulation is done in NS2Comparison between Self-stabilization,
Fault-containment and Improved Fault-containment
Simulation is done for NFC and FC faults as well as multiple FC faults occurring within CL
Performance is measured in terms of Beacon Intervals
NFC Fault Simulation Result
FC faults with distance greater than CL
FC faults with distance less than CL
Advantages & Disadvantages
If a fault can be contained, it is contained regardless of its occurrence in the network
Costs more communication overhead if a fault is not containable
References
Sukumar Ghosh, Arobinda Gupta, Sriram V. Pemmaraju. ”Fault-containing network protocols”. Proceedings of the 1997 ACM symposium on Applied computing, p.431-37, April 1997, San Jose, California, United States.
Sukumar Ghosh, Arobinda Gupta, T. Herman, Sriram V. Pemmaraju. Faultcontaining Self-Stabilizing Algorithms”. 15th Annual ACM Symposium on Principles of Distributed Computing, 1996, pp. 45-54.
References (Contd…)
Sandeep K. S. Gupta, Pradip K. Srimani. ”Self-stabilizing multicast protocols for ad hoc networks”. Journal of Parallel and Distributed Computing 63(1): 87-96 (2003)
Questions?