[TriLUG] OT: CDNs using DNS IPs to geolocate?

[Igor Partola]

They don't. But they can put address X in their North East DNS server,
address Y in their South West DNS server, and anycast the IP address for
the DNS servers. This way when your ISP's DNS server does a recursive
lookup it presumably goes to the nearest physical DNS server and gets
either address X or Y. At least I believe that's how that works. Perhaps
anycasting isn't necessary either, and there is some other way to do this.

Interestingly enough, if you use something like Google's DNS servers, then
a CDN might have a harder time determining your approximate location, so
you might end up talking to a CDN host that is located farther away from
you than the optimal one. See
http://www.lifehacker.com.au/2011/04/why-you-might-want-to-stick-with-your-isps-dns-server-after-all/for
example.

Igor


On Tue, Jan 7, 2014 at 1:02 PM, Brian <lugmail at cheetah.dynip.com> wrote:

> Hi Smart People,
>
> I recently came across the following sentence:
>
> "[L]arge content delivery networks (CDNs) like Akamai and LimeLight still
> use the IP address of the DNS server to judge your location."
>
> How does a CDN host know what DNS server I used to resolve their name?
>