A root server is part of the supporting infrastructure of the Internet, and facilitates Internet use by acting as the backbone of online access. Root servers are an essential part of the domain name system (DNS). They publish root zone file contents, which are responsible for DNS functionality, to the Internet. DNS associates information with domain names, and a great deal of online activity makes use of it. Domain names are mapped to IP addresses through this process, for example. A root server is often called a DNS root name server.