As we mentioned in the DNS overview, a resolver (if it doesn’t have any information in its cache) starts a query by asking the root nameservers. A resolver has a baked-in list of root nameservers (i.e., nameservers that are authoritative for the root domain .); in Posadis, this is done with the cache-ns construction; see caching in Posadis.

The standard root nameservers are run by the non-profit ICANN (Internet Corporation for Assigned Names and Numbers) organisation, which can decide what top-level domains are created, and where these are delegated to.

There is no reason though why a resolver couldn’t have another set of nameservers to start with. In fact, there are several alternate root nameservers available, that usually support more or different top-level domains. A list can be found in the Wikipedia article Alternate DNS root; some of the most well-known alternate root nameserver providers are the Open Root Server Confederation (ORSC), PacificRoot, and OpenNIC.