Comparing DNS Resolvers in the Wild Bernhard Ager Wolfgang M - - PowerPoint PPT Presentation

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Comparing DNS Resolvers in the Wild Bernhard Ager Wolfgang M - - PowerPoint PPT Presentation

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Comparing DNS Resolvers in the Wild Bernhard Ager Wolfgang M uhlbauer Georgios Smaragdakis Steve Uhlig { bernhard|steve|georgios } @net.t-labs.tu-berlin.de { wolfgang.muehlbauer@tik.ee.ethz.ch } Technische Universtit at Berlin/Deutsche

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Comparing DNS Resolvers in the Wild

Bernhard Ager Wolfgang M¨ uhlbauer Georgios Smaragdakis Steve Uhlig {bernhard|steve|georgios}@net.t-labs.tu-berlin.de {wolfgang.muehlbauer@tik.ee.ethz.ch}

Technische Universtit¨ at Berlin/Deutsche Telekom Laboratories ETH Z¨ urich

November 1 2010

Ager et al (TUB/DT Labs/ETH) Comparing DNS Resolvers in the Wild Nov 1 2010 1

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Motivation

Domain Name System (DNS)

DNS: resolve www.fg-inet.de to 85.214.78.63 Send HTTP request through Internet towards 85.214.78.63 ⇒ Fundamental building block of the Internet ⇒ Its performance is critical

Ager et al (TUB/DT Labs/ETH) Comparing DNS Resolvers in the Wild Nov 1 2010 2

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Motivation

Motivation

DNS according to the text book A commodity service: everyone is using it Resolves hostnames to IP addresses Same view from everywhere Caching Resolver assigned by ISP

Ager et al (TUB/DT Labs/ETH) Comparing DNS Resolvers in the Wild Nov 1 2010 3

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Motivation

Motivation

DNS according to the text book A commodity service: everyone is using it Resolves hostnames to IP addresses Same view from everywhere Caching Resolver assigned by ISP DNS in the wild New (mis)uses of DNS [Vixie’09]

Locality aware replies Dynamic load balancing NXDOMAIN catching Use as directory service

Third party resolvers, e. g., Google Public DNS and OpenDNS

[Vixie’09]

  • P. Vixie. What DNS is not. Commun. ACM, 52(12):43–47, 2009.

Ager et al (TUB/DT Labs/ETH) Comparing DNS Resolvers in the Wild Nov 1 2010 3

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Motivation

Motivation

DNS according to the text book A commodity service: everyone is using it Resolves hostnames to IP addresses Same view from everywhere Caching Resolver assigned by ISP DNS in the wild New (mis)uses of DNS [Vixie’09]

Locality aware replies Dynamic load balancing NXDOMAIN catching Use as directory service

Third party resolvers, e. g., Google Public DNS and OpenDNS DNS is changing ⇒ Study across content, locations and resolvers Compare DNS deployment of different ISPs and different resolvers Metrics: responsiveness and quality of replies

[Vixie’09]

  • P. Vixie. What DNS is not. Commun. ACM, 52(12):43–47, 2009.

Ager et al (TUB/DT Labs/ETH) Comparing DNS Resolvers in the Wild Nov 1 2010 3

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Data and Approach

Data and Approach

Overview Custom script 3 DNS resolvers: Google DNS, OpenDNS, local resolver 10k+ hostnames:

Popular content: Top 5000 from Alexa Less popular content: Bottom 2000 from Alexa Many objects on websites: 3000+ “embedded” hostnames

Two back-to-back queries for each hostname for each resolver ⇒ > 60 traces from all around the globe, > 50 different ISPs

Ager et al (TUB/DT Labs/ETH) Comparing DNS Resolvers in the Wild Nov 1 2010 4

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Results

First vs. second query time

The expected

10 20 50 100 500 2000 5000 10 20 50 100 200 500 2000 5000 Time for first query (ms) Time for second query (ms) GOOGLE LOCAL OPENDNS

Scatterplot 5000 ms timeout Minima indicate RTT to DNS server Small variance for second query due to caching ⇒ Local DNS apparently better than OpenDNS and GoogleDNS

Ager et al (TUB/DT Labs/ETH) Comparing DNS Resolvers in the Wild Nov 1 2010 5

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Results

First vs. second query time

The expected and the unexpected

10 20 50 100 500 2000 5000 10 20 50 100 200 500 2000 5000 Time for first query (ms) Time for second query (ms) GOOGLE LOCAL OPENDNS 10 20 50 100 500 2000 5000 10 20 50 100 500 2000 5000 Time for first query (ms) Time for second query (ms) GOOGLE LOCAL OPENDNS Ager et al (TUB/DT Labs/ETH) Comparing DNS Resolvers in the Wild Nov 1 2010 5

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Results

Impact of redirection

How many replies are in the same AS as the vantage point?

200 400 600 800 vantage points (sorted by # returned IPs that are in same AS) # returned IPs that are in same AS Google Local OpenDNS

Distant DNS servers CDN optimizes for resolver IP address Up to 1000 hosts with local resolval available not locally resolved with GoogleDNS/OpenDNS

Ager et al (TUB/DT Labs/ETH) Comparing DNS Resolvers in the Wild Nov 1 2010 6

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Summary

Summary

Summary Application performance depends on DNS deployment

Local DNS not always the performance champion But for content locality you have to use local DNS

DNS is a “battlefield” with many players How do we get to an open DNS system that can cope with today’s needs?

Ager et al (TUB/DT Labs/ETH) Comparing DNS Resolvers in the Wild Nov 1 2010 7

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Summary

Current work

Current work Repeat experiment in wider scope ⇒ Please help and run our new measurement script from

http://www.fg-inet.de/

at your home

No privacy implications

No interference with your personal data Source code fully open Manual trace upload

Little overhead

Ager et al (TUB/DT Labs/ETH) Comparing DNS Resolvers in the Wild Nov 1 2010 8

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Summary

Current work

Current work Repeat experiment in wider scope ⇒ Please help and run our new measurement script from

http://www.fg-inet.de/

at your home

No privacy implications

No interference with your personal data Source code fully open Manual trace upload

Little overhead

Questions?

Ager et al (TUB/DT Labs/ETH) Comparing DNS Resolvers in the Wild Nov 1 2010 8