The DNS is a hierarchical naming system for computers and other resources on the Internet, and is discussed in Ch. 9 of Understanding the Digital World.
DNS servers map domain names to IP addresses: when you type in a domain name (uoregon.edu), your browser gets the corresponding IP address from a DNS server.
This process starts with the Top-Level Domain (TLD), in this case .edu. As of July 2015, there are 1058 TLDs, including 301 country-code top-level domains (ccTLDs).
The IP addresses for all TLDs are stored on 13 Root Name Servers.
Logical vs Physical Root Name Servers
There are 13 logical (i.e., virtual) root name servers addresses which, through the use of anycast addressing, permits the actual number of physical root server instances to be much larger, and is 504 as of 17 January 2016.
(The choice of thirteen name servers was made because of limitations in the original DNS specification, which specifies a maximum packet size of 512 bytes.)
Where are the Physical Root Name Servers Located?
Ten servers were originally in the United States, and three servers were originally located in Stockholm (I-Root), Amsterdam (K-Root), and Tokyo (M-Root) respectively.
- Here is a map of the thirteen logical name servers, including anycasted instances.
- Top 20 DNS server map shows US internet dominance.
See Also
- Root Name Server (wikipedia)
- Internet Backbone (wikipedia)