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LEADER ELECTIONYu Meng09-25-2013

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OUTLINE Basic knowledge

Overview of Leader Election Complete Topology Logical Ring Topology Three Topology

Latest relevant knowledge Future works References

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BASIC KNOWLEDGE

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LEADER ELECTION Centralized Controller greatly simplifies

process synchronization A simple point failure can limit service

availability A new controller (the leader) can be chose

upon failure of the existing controller Known to all other processes in the group The initial of the system or a existing leader

failed The detection of failure is based on a time-

out

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ELECTION CRITERIA Extrema Finding

Based on a global priority

Preference-based leader election algorithm Processes in the group can vote for a leader

based on a personal-preference More general than Extrema Finding Resulting in more complex decision-making

outcome

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LEADER ELECTION VS. MUTUAL EXCLUSION Both try to reach an agreement for

identifying a unique process Differences:

A mutual exclusion must ensure that no process is starved, while a leader election is more concerned with the fast and successful termination of the election process

Leader election need to be announced to all processes

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COMPLETE TOPOLOGY Each process in the group can reach any

other process in one message hop Assumptions:

All process ids are unique and known to other process

Communication network is reliable and only the process may fail

A failure is reliable detected Each process as a global priority and the

highest-priority is elected leader

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BULLY ALGORITHM Extrema-finding algorithm Process with the highest-priority process as

the leader Bully Algorithm:

Process P starts a leader election if it suspects the failure of existing leader

P sends inquiry message to nodes with higher priority

If any response then, P gives up the election and waits for higher priority node to elect itself leader

If no response then P becomes a leader

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BULLY ALGORITHM

Process 4 detected leader failure and request an election

Process 5 and 6 response, then 4 stop Process 5 and 6 each hold a election

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BULLY ALGORITHM

Process 6 take the response and act as the leader

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LOGICAL RING TOPOLOGY Easy to construct Message initiated by node will return to itself Indicating completion of a round of operation

without the need for acknowledge Two phases:

Initiation: One process send an election message to its successors with its ID then each process add its own ID in the forwarding message

Leader election: Message come back to initiator then the initiator announce itself as leader and broadcast to others

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LOGICAL RING TOPOLOGY

Phase 1: Initiator Phase 2: Leader election

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TREE TOPOLOGIES A tree used for representing topological

structure

Each node is considered as an autonomous entity to exchange message with adjacent nodes

A minimum-weight spanning tree (MST) are employed

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TREE TOPOLOGY Gallager, Humbelt, and Spira’s algorithm is

based on searching and combining

Starting from each node and attaching level by level till it ends up with the MST

The last node that merges and yields to the final MST becomes the leader

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LATEST RELEVANT KNOWLEDGE

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RELEVANT RESEARCH In a distribution computing system or mobile network, leader

election is a very important issue. They propose a consensus-based leader election algorithm. By analyzing the mathematic analysis and algorithm simulation results, we notice that, when a new leader is elected, the proposed algorithm guarantees a consensus be reached while at the same time reducing the number of message passing.

(Chi-Chun Lo et. al., 2012)

Leader election in the presence of selfish nodes for intrusion detection in mobile ad hoc networks (MANETs). To balance the resource consumption among all nodes and prolong the lifetime of an MANET, nodes with the most remaining resources should be elected as the leaders. They justify the effectiveness of the proposed schemes through extensive experiments.

(Prabir Bhattacharya et. al., 2009)

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RELEVANT RESEARCH The space complexity: The necessary or sufficient number

of bits on processors to execute a leader election algorithm. Only one bit memory is sufficient for a leader election algorithm which is specific to a fixed n. A lower bound Omega(log n) on the space complexity, that is, it is impossible to construct a leader election algorithm if only log n bits are available for a processor.

(Masafumi Yamashita et. al., 2008)

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FUTURE WORKS

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FUTURE WORKS Apply the algorithm to cloud computing

problem

Dynamic consolidation of virtual machine with performance and energy trade-off

Virtual machine live migration with detecting failure of physical host

Possible application to detect the failure nodes under service level agreements

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REFERENCES1. Chow, Randy, et. al.,Distributed Operating Systems & Algorithms,

Addison Wesley, March 18, 19972. R. G. Gallager, P. A. Humblet, and P. M. Spira. "A Distributed Algorithm

for Minimum-Weight Spanning Trees". ACM Transactions on Programming Languages and Systems 5 (1): 66–77

3. Ephraim Korach, Shay Kutten, Shlomo Moran. "A Modular Technique for the Design of Efficient Distributed Leader Finding Algorithms".ACM Transactions on Programming Languages and Systems 12 (1): 84–101

4. DALAL, Y. Broadcast protocols in packet switched computer networks. Tech. Rep. 128, Dep. of Electrical Engineering, Stanford Univ., Apr. 1977

5. Mohammed, N. ; Otrok, H. ; Lingyu Wang ; Debbabi, M. ; Bhattacharya, P. ,Mechanism Design-Based Secure Leader Election Model for Intrusion Detection in MANET.Dependable and Secure Computing, IEEE Transactions on, 2011, 89-103

6. HUMBLET, P.A. A distributed algorithm for minimum weight directed spanning trees. Rep LIDS-P-1149, Laboratory for Information and Decision Systems, Massachusetts Inst. of Technology, Cambridge, Mass., Sept. 1981

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REFERENCES7. Hsu-Chia Cahng ; Chi-Chun Lo, "A Consensus-Based Leader

Election Algorithm for Wireless Ad Hoc Networks" Computer, Consumer and Control (IS3C), 2012 International Symposium, 2012 , 232- 235

8. LAWLER, E. Combinatorial Optimization-Networks and Matroids. Holt, Rinehart & Winston, New York, 1976.

9. LIU, C.L. Introduction to Combinatorial Mathematics. McGraw Hill, New York, 1968

10. PRIM, R.C. Shortest connection networks and some generalizations. Bell Syst. Tech. J. 36 (1957), 1389-1401.

11. YAO, A.C.C. An O(E log log V) algorithm for finding minimum spanning trees. Inf. Process. Lett. 4 (1975), 21-23

12. Andot, E. ; Ono, H. ; Sadakane, K. ; Yamashita, M. “The space complexity of the leader election in anonymous networks” Parallel and Distributed Processing, 2008 , 1-8

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Thank you!