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Relative Network Positioning via CDN Redirections

Relative Network Positioning via CDN Redirections. A. Su, D. Choffnes , F. Bustamante, A. Kuzmanovic ICDCS 2008 Presented by: Imranul Hoque. Relative Network Positioning. Replica 2. Replica 1. Replica 3. How to calculate RTT?. Which one to choose?. Relative Position. 1. Replica 2

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Relative Network Positioning via CDN Redirections

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  1. Relative Network Positioning via CDN Redirections A. Su, D. Choffnes, F. Bustamante, A. Kuzmanovic ICDCS 2008 Presented by: ImranulHoque

  2. Relative Network Positioning Replica 2 Replica 1 Replica 3 How to calculate RTT? Which one to choose? Relative Position 1. Replica 2 2. Replica 1 3. Replica 3 Client RTT(C, R2) < RTT(C, R1) < RTT(C, R3)

  3. Relative Network Positioning (2) Replica 2 Replica 1 Replica 3 PING PING PING Client Problems?

  4. Relative Network Positioning (3) N 1 N 8 x8, y8 x1, y1 PING N 2 N 7 x2, y2 x7, y7 PING N 3 PING N 6 x3, y3 x6, y6 N 4 N 5 x5, y5 x4, y4

  5. 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

  6. Content Delivery Network GET yahoo.com GET yahoo.com R3 R5 R1 R4 Client 1 Client 2 R2 GET yahoo.com CDN performs extensive measurement to redirect clients to closest replicas Client 3

  7. Network Positioning via CDN R3 R5 R1 R4 N1 N4 R2 0, 0, 10, 20, 70 70, 30, 0, 0 , 0 N3 N2 0, 0, 0, 80, 20 Clusters 50, 50, 0, 0 , 0

  8. Evaluation • Closest node selection • Clustering • PlanetLab experiment

  9. Closest Node Selection foxnews.comyahoo.com foxnews.comyahoo.com AKAMAI Who is the closest of the 240 nodes? Server: 240 PlanetLab nodes Client: 1000 DNS Servers from King data November 2006 & January 2007

  10. 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)

  11. Closest Node Selection (3) How can they be similar?

  12. Closest Node Selection (4) CRP outperforms Meridian 25% of the time 65% nodes differ < 7 ms

  13. Clustering foxnews.comyahoo.com AKAMAI 177 broadly distributed DNS servers

  14. Clustering (2) • Compare CRP based clustering to: • ASN-based clustering • Metrics • Quality of cluster Inter-cluster latency Intra-cluster latency

  15. Clustering (3) Plot is very misleading!

  16. Clustering (4) Total Clusters: 16 (ASN), 36 (CRP)

  17. Conclusion • CDN based relative network positioning • Avoids direct probing • Lightweight • Highly scalable • If two nodes are not redirected to common set of servers, then no way to know about their proximity • Experimental plots hide lots of details

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