Root zone file

At the top of the domain name system is the root zone file, which directs Internet Protocol number queries to other domain name system databases called top-level domain zone files. Because of the large volume of requests to link domain names with Internet Protocol numbers, both root zone files and top-level domain zone files are replicated on a number of different computers, thus ensuring both speed and consistency.

The master root server is called the “authoritative root server” or the “A” root server. There are 12 other root servers located worldwide (designated "B" through "M"), and each receives updated information daily from the “A” root server regarding the contents of the root zone file and the top-level domain zone files.