ptp. Soo-Bae Kim 4/09/02 isdl@snu. What is peer to peer?. Communication without server advantage No single point of failure Easy data sharing disadvantage No service quality guarantee Increased network traffic . Outline. Chord? Chord protocol simulation and experiment result
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path length= hops
improve routing fault tolerance owing to having more next hops.Multi-dimension coordinate spaces.
Contents of the hash table are replicated on every realities.
Improve routing falult tolerance,data availability and and path lengthRealities:multiple coordinate spaces
Reducing average query latency
but increasing the size of the database and query traffic by a k factor.Multiple hash function
Latency stretch: ratio of the latency on the CAN network to the average latency on the IP network.Topologically-sensitive construstion of CAN overlay network
Achieve load lancing. landmarks.
Not sufficient for true load balancing because some pairs will be more popular than others : hot spot
V = (entire coordinate space:Vt) / (node:n)More uniform partitioning
Many Web clients are behind proxies or firewalls.so IP address seen by the external network may actually correspond to a proxy.
Whois,traceroute (GeoTrack) network delay measurement (Geoping)Due to proxies
University host : don’t use proxy address seen by the external network may actually correspond to a proxy.
FooTV host : behind proxy
NetGeo : Whois based network mapping tool
GeoTrack : 590 km
NetGeo : 650 kmPerformance(GeoTrack & NetGeo)
Presence of circuitous geographic paths and bottlenecks. address seen by the external network may actually correspond to a proxy.
But ,in recent years, provide richer connectivity with wide bandwidth.
From several known locations to hosts in the univ.
linearized distance:sum of the lengths of the individual hopsConsider component
Perform traceroute and pong measurement from 14 different sources to 256 university servers.
For small delay value(<10ms),most of the hosts(>90%) correct.
But for large value delay(>40ms), provide 70% confidence.(error of at least 300~400km)CDF of distance
Given a new target host T,first measure the network delay from N probes.
Next find the nearest neighbor in delay map using Eucledian distance
several percent levels of error distance as a function of a number of probes
Having 7 to 9 probes would be ideal for NNDS.
Well-distributed probe yield better accuracyNNDS
Locating host in univhost from N probes.
Locating hosts in bCentralExperiment result
Importance of sub-clustering from N probes.
/24 cluster : ignore BGP
BGP+subclustering is best performanceExperiment result