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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

Relative Network Positioning via CDN Redirections

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

ICDCS 2008

Presented by: ImranulHoque


Relative network positioning
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)


Relative network positioning 2
Relative Network Positioning (2)

Replica 2

Replica 1

Replica 3

PING

PING

PING

Client

Problems?


Relative network positioning 3
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


Relative network positioning 4
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


Content delivery network
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


Network positioning via cdn
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


Evaluation
Evaluation

  • Closest node selection

  • Clustering

  • PlanetLab experiment


Closest node selection
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


Closest node selection 2
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)


Closest node selection 3
Closest Node Selection (3)

How can they be similar?


Closest node selection 4
Closest Node Selection (4)

CRP outperforms Meridian 25% of the time

65% nodes differ < 7 ms


Clustering
Clustering

foxnews.comyahoo.com

AKAMAI

177 broadly distributed DNS servers


Clustering 2
Clustering (2)

  • Compare CRP based clustering to:

    • ASN-based clustering

  • Metrics

    • Quality of cluster

Inter-cluster

latency

Intra-cluster

latency


Clustering 3
Clustering (3)

Plot is very misleading!


Clustering 4
Clustering (4)

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


Conclusion
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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