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I thought there wasn't one single root, but 13? And aren't root DNS servers already de-centralized geographically and using anycast?

Here is the map of current root servers: http://en.wikipedia.org/wiki/File:Root-current.svg

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Yes and no. There are 13 'installations' (essentially IPs), some anycasted, but they all serve the same contents that are provided by the ICANN. So they are one conceptual root, albeit a geographically distributed one. The IETF has worked hard to make it robust (successfully so far), but the fact remains that 13 hardcoded IPs and one file that comprise the root of the DNS system.

http://en.m.wikipedia.org/wiki/DNS_root_zone has some details.

Those 13 IPs aren't as hard coded as you suggest. They typically ship with the DNS server software (ISC bind for example) but these are updated at regular intervals. As long as all 13 IPs aren't changed at once you could quite easily transition from one set of IPs to others. In ISC bind this root "cache" even has its own zone type; "hint".

Thanks, I wasn't aware they changed regularly. From what I can find, 4 v4 IPs have changed since 1997, plus the addition of a number of v6 IPs over the years. I'd be curious to know the last time all IPs were different, if ever.

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