impact of neighbor selection on performance and resilience of structured p2p networks iptps feb. 25,...
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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
Unbalanced Overlay Structure
• CDF of node degrees of a 205-node Bamboo overlay running on PlanetLab
Talk Outline
• Motivation– Impact of neighbor selection on resilience
• Neighbor selection model
• Simulation setup
• Performance
• Static resilience
• Redundancy
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
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
Neighbor Selection Model
Model Cost of node i
Random N/A
Dist (PNS) ∑edgecost(i,nbr)
Cap ∑nodecost(nbr)
CapDist ∑[edgecost(i,nbr) + nodecost(nbr)]
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)
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
Hybrid Achieves Resilience against Targeted Attacks
Chord (12 sequential neighbors)Tapestry (2 random backup links)
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
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
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