Dave Naffziger's Blog

In tech circles the belief that consumer ISP DNS servers are terrible is widely accepted. So, I found this study fascinating. The quick takeaway is that Content Distribution Networks (CDNs) like Akamai rely heavily on the location of the DNS server to select the server to serve content from. Websites that rely on CDNs to serve some content load slower because the CDN chooses a suboptimal server. And nearly every major website uses CDNs for some of their content.

I ran the test script from my home comcast cable connection. In my case, the CDN server returned by OpenDNS was the slowest in both tests, while Google’s was the fastest. Here is the data from my test of Akamai’s CDN (summarized for readability):

>>> test(‘profile.ak.fbcdn.net’, ‘Akamai’) == testing : profile.ak.fbcdn.net Akamai =======
testing : OpenDNS ( 208.67.222.222 )
204.2.171.82

Ping statistics for 204.2.171.82:
Approximate round trip times in milli-seconds:
Minimum = 46ms, Maximum = 48ms, Average = 47ms
—————————————————
testing : Google ( 8.8.8.8 )
96.17.69.66

Ping statistics for 96.17.69.66:
Approximate round trip times in milli-seconds:
Minimum = 11ms, Maximum = 13ms, Average = 12ms
—————————————————
testing : default ( 68.87.69.150 )
96.17.70.16

Ping statistics for 96.17.70.16:
Approximate round trip times in milli-seconds:
Minimum = 36ms, Maximum = 38ms, Average = 37ms
—————————————————
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On closer inspection, the Akamai node that serves my content varies by DNS solution used (I’m in Seattle):

DNS Provider	Akamai Node Used
OpenDNS	Los Angeles
Google	Seattle
Comast	Seattle

Conclusion

The author of the original post makes a great point. The location that CDNs use to serve content impacts browsing experience much more so than the speed at which DNS resolves an unknown domain. The DNS server used for the request can have a big impact in the selection made.

In my specific instance, Google’s DNS sends me to the best CDN node (at least for Akamai and Internap)

An IP Geolocation Aside

At Quova, we primarily sold against Akamai’s EdgeSuite service which provided some geolocation data. One of the common myths that Akamai sales staff liked to propagate was that Akamai’s data must be better because of the thousands of Akamai CDN servers.

We would usually respond that CDNs primarily depended on network topology, not user geography. Therefore the many CDN servers Akamai used provided no benefit to the core IP geolocation data. I think if I had known how much Akamai depends on DNS sever location, our counter-arguments might have been stronger.