L EADER E LECTION Yu Meng

O UTLINE Basic knowledge Overview of Leader Election Complete Topology Logical Ring Topology Three Topology Latest relevant knowledge Future works References 2

B ASIC KNOWLEDGE 3

L EADER 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 4

E LECTION C RITERIA 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 5

L EADER ELECTION VS. M UTUAL E XCLUSION 6 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

C OMPLETE 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 7

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 8

B ULLY A LGORITHM 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 9

B ULLY ALGORITHM Process 6 take the response and act as the leader 10

L OGICAL 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 11

L OGICAL RING TOPOLOGY 12 Phase 1: Initiator Phase 2: Leader election

T REE 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 13

T REE 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 14

L ATEST RELEVANT KNOWLEDGE 15

R ELEVANT 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) 16

R ELEVANT 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) 17

F UTURE WORKS 18

F UTURE 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 19

R EFERENCES 1. Chow, Randy, et. al.,Distributed Operating Systems & Algorithms, Addison Wesley, March 18, 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– DALAL, Y. Broadcast protocols in packet switched computer networks. Tech. Rep. 128, Dep. of Electrical Engineering, Stanford Univ., Apr 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, 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

R EFERENCES 7. 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, LAWLER, E. Combinatorial Optimization-Networks and Matroids. Holt, Rinehart & Winston, New York, LIU, C.L. Introduction to Combinatorial Mathematics. McGraw Hill, New York, PRIM, R.C. Shortest connection networks and some generalizations. Bell Syst. Tech. J. 36 (1957), YAO, A.C.C. An O(E log log V) algorithm for finding minimum spanning trees. Inf. Process. Lett. 4 (1975), Andot, E. ; Ono, H. ; Sadakane, K. ; Yamashita, M. “The space complexity of the leader election in anonymous networks” Parallel and Distributed Processing, 2008,

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