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1 Fury Route Leveraging CDNs to Remotely Measure Network Distance Marcel Flores Alexander Wenzel Kevin Chen Aleksandar Kuzmanovic

Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

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Page 1: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

1

Fury RouteLeveraging CDNs to Remotely

Measure Network Distance

Marcel FloresAlexander WenzelKevin ChenAleksandar Kuzmanovic

Page 2: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Relative network distance• Which provider is closer

to the client?

• Enable systems to make a best-guess prior to the first communication.

• Can we do it without infrastructure or host participation?

2

Client

Provider A

Provider B

Page 3: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Relative network distance

• Peer and server selection.

• Large scale Internet measurement, allows understanding of hosts beyond control.

• Clients which can’t be subjected to direct measurements (i.e. traffic sensitive, unreachable).

3

Page 4: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Use CDN replica selection• CDNs provide end users with a

“nearest” replica.

• Helps to reduce user-experienced latency.

• Often selected via DNS.

• Providers include: Google, Edgecast, Alibaba, CDN77, CloudFront, CDNetworks, Adnxs

• Varying response granularity

4

Page 5: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

EDNS Client Subnet• Allows DNS requests to include an origin subnet.

• Simplifies replica selection procedure.

• Further provides a scope, indicating the specificity of the response.

5

Allows for queries as arbitrary hosts.

Page 6: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Build a graph• Construct a directed graph G = (V, E)

• V = Set of hosts (client, provider, replicas)

• E = Set of of CDN replica response relationships

• weight(A, B) = 32 - scope (a, b)

6

8

10CDN Responses}

Page 7: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Build a graph

7

Arizona

Rutgers

Cloudfront - LAX

Google - DFW

88 Google - LGA

CDN77 - NY

10

8

Page 8: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Forward progress• How do we know which candidate to select?

• Ask coarse-grained providers which replica they would serve to each candidate.

• Further ask which replicas they would serve the target set.

• Measure the overlap in responses.

8

Page 9: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Build a graph

9

Arizona

Rutgers

Cloudfront - LAX

Google - DFW

88 Google - LGA

CDN77 - NY

10

8

Page 10: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Build a chain

10

Arizona

Rutgers

Cloudfront - LAX

Google - DFW

88

Google - LAX

8

Google - LGA

CDN77 - NY

10

8

16

UCLA

8

Page 11: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Why does it work?• Ultimately reveals the underlying infrastructure of

the CDN Deployments.

• Low-density deployments will indicate large distances.

• Not all deployments are the same.

• ECS responses are more than just noise.

11

Page 12: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Accuracy

14

Origin

Targets1) Measure ping time

2) Construct chains

3) Compare pairs

4) Count matches

Page 13: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Accuracy

• Filter by minimum difference:

• All, 25, 50, 100ms differences.

15

20

21 75

• What about very similar distances?

Page 14: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Accuracy

16

Median 83% correct

Best

Page 15: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Caching• Would like to build a consistent graph that expands

as we see more hosts.

• How significantly does this graph actually reduce the queries?

17

Page 16: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Caching

After 20 paths, chains complete with under 50 queries18

Page 17: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Summary

• Developed a system which provides an estimate of relative network distance.

• Correctly determines 83% of relative distances in the median case.

• After a cache is established, the majority of chains can be built with under 50 queries.

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Page 18: Leveraging CDNs to Remotely Measure Network Distance · Use CDN replica selection •CDNs provide end users with a “nearest” replica. •Helps to reduce user- experienced latency

Thank you!