Impact of Neighbor Selection on Performance and Resilience of Structured P2P Networks

1. Impact of Neighbor Selection on Performance and Resilience of Structured P2P Networks IPTPS Feb. 25, 2005 Byung-Gon Chun, Ben Y. Zhao, and John Kubiatowicz UC Berkeley and UC Santa Barbara

2. Structured P2P Overlay Berkeley Berkeley MIT Source 11… 00… 10… 01… Destination

3. Unbalanced Overlay Structure • CDF of node degrees of a 205-node Bamboo overlay running on PlanetLab

4. Talk Outline • Motivation • Impact of neighbor selection on resilience • Neighbor selection model • Simulation setup • Performance • Static resilience • Redundancy

5. Routing Details • Chord (ring geometry) • Each node forwards to the live neighbor that is closest to the destination in the identifier space • The lookup fails if all neighbors before the destination in the identifier space fail • Tapestry (tree geometry) • Each node forwards messages to the first live neighbor matching one more prefix digit • The lookup fails, if all primary and backup links in the routing entry fail

6. Neighbor Selection Model • Neighbor selection is a cost minimization problem pathcost(src,dst) = edgecost(src,nbr) + nodecost(nbr) + remaining_pathcost(nbr, dst) edgecost: network latency, nodecost: processing delay

7. Neighbor Selection Model

8. Simulation Setup • A neighbor is chosen among 32 sample nodes • 5100 node transit-stub physical networks • 4096 overlay nodes at random physical locations • 3 topologies and 3 overlay node placements • Node capacity model • Coarse-grained uniform distribution : pick a processing delay randomly among (/10, 2/10, .., ) where  is the maximum processing delay in seconds • Bimodal distribution (fast and slow nodes)

9. Performance under Uniform Processing Delay Distribution

10. Failure and Attack Model • Random node failures • Choose a fraction of nodes randomly • Targeted node attacks • Sort nodes with in-degree, remove nodes with high in-degree first • Resilience metric • Failed paths: proportion of all pairs of live nodes that cannot route to each other via the overlay after a failure or attack event

11. Random Node Failures Tapestry (tree) Chord (ring)

12. Targeted Node Attacks Tapestry (tree) Chord (ring)

13. Redundancy (Random links) Backup links Sequential neighbors

14. Hybrid Achieves Resilience against Targeted Attacks Tapestry (2 random backup links) Chord (12 sequential neighbors)

15. Related Work • Gummadi et al. (SIGCOMM 2003) • Routing geometry • PNS, PRS • Random node failures • Castro et al. (OSDI 2002) • Eclipse attacks - fake proximity • Two routing tables: proximity-based and constrained • Singh et al. (SIGOPS EW 2004) • Node degree bounding • Albert, Jeong, and Barabasi (Nature, 2000) • Power-law graph • Chun et al. (INFOCOM 2004) • Selfishly constructed overlay

16. Conclusion • Neighbor selections that consider network proximity and node capacity improve routing performance • Such neighbor selections do not affect resilience against random failures • These performance benefits come with loss in attack tolerance • Adding redundancy (w. randomness) can shield against targeted attacks

17. Impact of Neighbor Selection on Performance and Resilience of Structured P2P Networks IPTPS Feb. 25, 2005 Byung-Gon Chun, Ben Y. Zhao, and John Kubiatowicz UC Berkeley, UC Santa Barbara