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# Relative Network Positioning via CDN Redirections - PowerPoint PPT Presentation

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

A. Su, D. Choffnes, F. Bustamante, A. Kuzmanovic

ICDCS 2008

Presented by: ImranulHoque

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)

Replica 2

Replica 1

Replica 3

PING

PING

PING

Client

Problems?

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

• 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

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

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

• Closest node selection

• Clustering

• PlanetLab experiment

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

• 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)

How can they be similar?

CRP outperforms Meridian 25% of the time

65% nodes differ < 7 ms

foxnews.comyahoo.com

AKAMAI

• Compare CRP based clustering to:

• ASN-based clustering

• Metrics

• Quality of cluster

Inter-cluster

latency

Intra-cluster

latency

Total Clusters: 16 (ASN), 36 (CRP)

• 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