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Relative Network Positioning via CDN Redirections
A. Su, D. Choffnes, F. Bustamante, A. KuzmanovicICDCS 2008
Presented by: Imranul Hoque
2
Relative Network Positioning
Replica 3Replica 2Replica 1
Client
Which one to choose?
1. Replica 22. Replica 13. Replica 3
Relative Position
RTT(C, R2) < RTT(C, R1) < RTT(C, R3)
How to calculate RTT?
4
Relative Network Positioning (3)
N 1
PINGN 2
N 3
N 4 N 5
N 6
N 7
N 8
PING
PING
x2, y2
x3, y3
x4, y4 x5, y5
x6, y6
x7, y7
x1, y1 x8, y8
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Relative Network Positioning (4)
• Network Coordinates– Scalable but error prone– Error minimization requires frequent probing– Frequent probing incurs extra overhead
• Relative order is more important than absolute distances
Leverage CDN to deduce relative position
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Content Delivery Network
Client 1 Client 2
Client 3
GET yahoo.com
GET yahoo.com
GET yahoo.com
R1
R2
R3
R4
R5
CDN performs extensive measurement to redirect clients to closest replicas
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Network Positioning via CDN
N1 N4
N3
R1
R2
R3
R4
R5
N2
70, 30, 0, 0 , 0
50, 50, 0, 0 , 00, 0, 0, 80, 20
0, 0, 10, 20, 70
Clusters
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Closest Node Selection
Client: 1000 DNS Servers from King data
Server: 240 PlanetLab nodes
AKAMAI
Who is the closest of the 240 nodes?
foxnews.comyahoo.com
foxnews.comyahoo.com
November 2006 & January 2007
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Closest Node Selection (2)
• Compare the performance of CDN based approach (CRP) to:– Active measurement– Meridian
• Metrics– Latency to the closest server (Meridian vs. CRP)– Relative error (Meridian vs. CRP)
14
Clustering (2)
• Compare CRP based clustering to:– ASN-based clustering
• Metrics– Quality of cluster
Inter-clusterlatency
Intra-clusterlatency