Since 2016, the root zone has been overseen by the Internet Corporation for Assigned Names and Numbers (ICANN) which delegate the management to a subsidiary acting as the Internet Assigned Numbers Authority (IANA). Distribution services are provided by Verisign. Prior to this, ICANN performed management responsibility under oversight of the National Telecommunications and Information Administration (NTIA), an agency of the United States Department of Commerce.
A combination of limits in the DNS definition and in certain protocols, namely the practical size of unfragmented User Datagram Protocol (UDP) packets, resulted in a practical maximum of 13 root name server addresses that can be accommodated in DNS name query responses. However the root zone is serviced by several hundred servers at over 130 locations in many countries.
The DNS root zone is served by thirteen root server clusters which are authoritative for queries to the top-level domains of the Internet. Thus, every name resolution either starts with a query to a root server or uses information that was once obtained from a root server.
The root servers clusters have the official names a.root-servers.net to m.root-servers.net. To resolve these names into addresses, a DNS resolver must first find an authoritative server for the net zone. To avoid this circular dependency, the address of at least one root server must be known for bootstrapping access to the DNS. For this purpose operating systems or DNS server or resolver software packages typically include a file with all addresses of the DNS root servers. Even if the IP addresses of some root servers change, at least one is needed to retrieve the current list of all name servers. This address file is called named.cache in the BIND name server reference implementation. The current official version is distributed by ICANN's InterNIC.
With the address of a single functioning root server, all other DNS information may be discovered recursively, and information about any domain name may be found.
Courtesy of Wikipedia
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