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I understand the root DNS servers (A to M). What I don't exactly get it is the difference between, let's say the "F Root DNS" and the "A Root DNS".

Why is there 49 total "F" DNS's and only "A" DNS's?

Isn't the DNS record database from A to M the same?

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2 Answers 2

up vote 5 down vote accepted

Because of vital importance, high load and especially because of need to tolerate any possibly DDoS attack, internet have many root servers.

All root servers store the same DNS database.

A through M is total of 13 nameservers, but to be exact each this "nameserver" is not actually a server, but it is an IP address.

For most of root servers, that IP address corresponds not to single machine, but it is a so-called anycast address - address which can be routed to any of several locations around the globe. Thus when you query, say f.root-servers.net, your query may be answered by a server located at any of this anycast sites (usually the one nearest to your).

"A" root server is also anycasted.

Different root servers (A, F etc.) operated by different organisations, thus lowering possibility of some human mistake to take down the whole internet.

There's a map of root server locations on root-servers.org.

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Thanks for your meaningful feedback. Now I'm clear that each letter corresponds to an independent entity that manages it that specific Root DNS. –  Andre Apr 3 '12 at 14:16

Georedundancy, in short.

Root queries use anycasting to select a closeby root instance.

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Hi, and the database record between an "A" and "F" is EXACTLY the same? –  Andre Apr 3 '12 at 12:41
    
What "record" ? –  adaptr Apr 3 '12 at 12:42
    
Why there is an "I" and "F" in the same city (JHB / South Africa) ? –  Andre Apr 3 '12 at 12:42
    
The root nameservers are not georedundant - the servers BEHIND them are. –  adaptr Apr 3 '12 at 12:48
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There's "I" in JHB because "Autonomica" decided to have a server in JHB, and there's "F" in JHB because ISC decided to have a server there. 1. Operators don't really have to be tightly coordinated. 2. The best would be to have any of the X.root-servers.net at any location - it improves resolution speed. –  Sandman4 Apr 3 '12 at 13:06

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