Resolver Operation
When a computer on the Internet needs to resolve a domain name, it uses resolver software to perform the lookup. A resolver breaks the name up into its labels from right to left. The first component (TLD) is queried using a root server to obtain the responsible authoritative server. Queries for each label return more specific name servers until a name server returns the answer of the original query.
In practice, most of this information does not change very often over a period of hours and therefore it is cached by intermediate name servers or by a name cache built into the user's application. DNS lookups to the root nameservers may therefore be relatively infrequent. A survey in 2003 reports that only 2% of all queries to the root servers were legitimate. Incorrect or non-existent caching was responsible for 75% of the queries, 12.5% were for unknown TLDs, 7% were for lookups using IP addresses as if they were domain names, etc. Some misconfigured desktop computers even tried to update the root server records for the TLDs. A similar list of observed problems and recommended fixes has been published in RFC 4697.
Although any local implementation of DNS can implement its own private root name servers, the term "root name server" is generally used to describe the thirteen well-known root name servers that implement the root name space domain for the Internet's official global implementation of the Domain Name System.
Read more about this topic: Root Name Server
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