Kalman Graffi - IEEE NetSys 2013 - Ca-Re-Chord - A Churn Resistant Self-stabilizing Chord Overlay Network

852 views

Published on

Kalman Graffi - IEEE NetSys 2013 - Ca-Re-Chord - A Churn Resistant Self-stabilizing Chord Overlay Network

Published in: Education, Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
852
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
5
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Kalman Graffi - IEEE NetSys 2013 - Ca-Re-Chord - A Churn Resistant Self-stabilizing Chord Overlay Network

  1. 1. Markus Benter, Mohammad Divband, Sebastian Kniesburges, Andreas Koutsopoulos, Kalman Graffi University of Paderborn 1 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Networked Systems 2013
  2. 2. University of Paderborn 2 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network 1. Chord 2. Re-Chord 3. Ca-Re-Chord 4. Evaluation 5. Conclusion Overview
  3. 3. University of Paderborn 3 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Chord [Stoica et al., 2001]
  4. 4. University of Paderborn 4 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network • DHT (Distributed Hash Table) • Node degree: O(log(n)) • Routing performance: O(log(n)) Chord
  5. 5. University of Paderborn 5 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network • Chord network partitioned (due to churn) • E.g. two Chord rings • Successors and predecessors locally consistent • Cannot be detected Chord: Inconsistency Issue
  6. 6. University of Paderborn 6 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Re-Chord [Kniesburges et al., 2011]
  7. 7. University of Paderborn 7 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Re-Chord: Self-Stabilizing Chord
  8. 8. University of Paderborn 8 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Re-Chord: State
  9. 9. University of Paderborn 9 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network • Edges: • Each node has successor and predeccessor • Each real node has real right neighbor and real left neighbor Re-Chord: State
  10. 10. University of Paderborn 10 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Re-Chord: State
  11. 11. University of Paderborn 11 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network In stable state, Chord is subgraph of Re-Chord Re-Chord: State
  12. 12. University of Paderborn 12 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Six stabilization rules are necessary: 1. Create and Delete Virtual Nodes 2. Overlapping Neighborhood 3. Closest Real Neighbor 4. Linearization 5. Ring Edge 6. Connection Edges Provable: Network is weakly connected then eventually be in stable state after finite number of steps Re-Chord: Stabilization Rules
  13. 13. University of Paderborn 13 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network 1. Create and Delete Virtual Nodes
  14. 14. University of Paderborn 14 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network 3. Closest Real Neighbor
  15. 15. University of Paderborn 15 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network • Theorem: Can be found in O(log(n)) steps • Each node has O(log(n)) virtual nodes • Number of virtual nodes between two real nodes O(log(n)) • Worst-Case is O(„number of contiguous virtual nodes“) • Analysis in paper 3. Closest Real Neighbor
  16. 16. University of Paderborn 16 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network • Rule: Propagate all edges (but the two closest neighbors) • Provable: Graph becomes a line after O(n) steps 4. Linearization
  17. 17. University of Paderborn 17 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network 5. Ring Edge
  18. 18. University of Paderborn 18 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network • Weakly connected graph: stable after O(n log(n)) rounds • Node joins: stable after O(log2(n)) rounds • Node leaves: stable after O(log(n)) rounds Re-Chord: Analysis Too slow in contiguous churn szenarios Ca-Re-Chord Churn Aware Re-Chord
  19. 19. University of Paderborn 19 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Ca-Re-Chord: Idea
  20. 20. University of Paderborn 20 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Ca-Re-Chord: Build up
  21. 21. University of Paderborn 21 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network • Apply quick-fixing in two situations • Ping fails • Message transmission fails (re-transmit) • Quickfix can fix... • The embedded Chord ring (applied on real nodes) • The finger representations (applied on virtual nodes) • Quickfixing can improve two things • Speed-up self-stabilization • Improve message delivery directly (message re-transmission) • How to choose k? Should depend on... • Node failure rate • Desired robustness against churn (increases with k) • Acceptable message overhead (increases with k) Ca-Re-Chord: Properties
  22. 22. University of Paderborn 22 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Ca-Re-Chord: Churn resistance
  23. 23. University of Paderborn 23 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Evaluation
  24. 24. University of Paderborn 24 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network • PeerfactSim.KOM • Realistic P2P network simulator • Implementation of ... • Chord • Re-Chord • Ca-Re-Chord • Settings • Initial Network Size: 1000 Nodes • Successors k=3 • Drop packet after 50 hops • Exponential churn • Mean session length = 60 min • Adjustable churn factor (?) • Let nodes join (60 min), churn after stabilization (1400 min) Ca-Re-Chord: Evaluation
  25. 25. University of Paderborn 25 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Ca-Re-Chord: Evaluation (churn factor ???) axis
  26. 26. University of Paderborn 26 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Ca-Re-Chord: Evaluation
  27. 27. University of Paderborn 27 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Ca-Re-Chord: Evaluation (Unklar)
  28. 28. University of Paderborn 28 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Conclusion
  29. 29. University of Paderborn 29 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network • Re-Chord • Self-stabilizing: Recover from every weakly connected graph • Not robust against churn • Stabilization too slow • Ca-Re-Chord • Extends Re-Chord • Goal: churn resilience • Apply k-successor quickfixing before stabilization • Disadvantage: additional traffic (maintaining k links) • Evaluation: Ca-Re-Chord as good as Chord Conclusion
  30. 30. University of Paderborn 30 Ca-Re-Chord A Churn Resistant Self-stabilizing Chord Overlay Network Tank you for your attention

×