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A root nameserver is a DNS server that answers requests for the root namespace domain, and redirects requests for a particular Top-level Domain to that TLD's nameservers. All domain names on the address. The empty String after the final dot is called the Root Domain , and all other domains (i.e. .com, .org, .net, etc.) are contained within the root domain. When a computer on the Internet wants to resolve a domain name, it works from right to left, asking each nameserver in turn about the element to its left. The root nameservers (which have responsibility for the . domain) know about which servers are responsible for the top-level domains. Each top-level domain (such as .org) has its own set of servers, which in turn delegate to the nameservers responsible for individual domain names (such as wikipedia.org), which in turn answer queries for IP addresses of subdomains or hosts (such as www). In practice, most of this information doesn't change very often and gets cached, and ''necessary'' DNS lookups to the root nameservers are relatively rare. However, there are a lot of incorrectly configured systems on the Internet that cause most of the traffic to the root servers. For example, queries with the source address 0.0.0.0 (corresponding to anywhere and everywhere) make it to the root servers. Also, misconfigured desktop computers sometimes try to update the root server records for the TLDs, which is incorrect. See the Bogus Queries in the external links for more amusing stories. There are currently 13 root name servers, with names in the form ''letter''.root-servers.net where ''letter'' ranges from A to M : Older servers had their own name before the policy of using similar names was established. No more names can be used because of protocol limitations - UDP packet can only carry 512 bytes reliably and a hint file with more than 13 servers would be larger than 512 bytes - but the C, F, I, J and K servers now exist in multiple locations on different continents, using Anycast announcements to provide a decentralized service. As a result most of the physical, rather than nominal, root servers are now outside the United States. There are quite a few alternative namespace systems with their own set of root nameservers that exist in opposition to the mainstream nameservers. The first, AlterNIC , generated a substantial amount of press. See Alternative DNS Root for more information. SEE ALSO EXTERNAL LINKS
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