DNS (Domain Name System)

DNS (Domain Name System) – is a system of names officially assigned to individual networks and servers on the Internet as an easier method of remembering those names than a string of IP numbers. For example: www.agnitum.com is easier to remember than the IP address 207.44.236.84. The DNS service automatically translates the name to its corresponding IP address. The DNS system requires a static configuration of its tables, which define the one to one correspondence of computer names and IP addresses.

The DNS protocol is an auxiliary service protocol at the application level. This protocol is an asymmetric one – DNS servers and DNS clients are defined in it. DNS servers store a part of the distributed database that contains the correspondence of names and IP addresses. This database is distributed according to administrative domains on the Internet. Clients of the DNS server know the IP address of the server of their administrative domain and they transfer a request with the DNS name according to the IP protocol, and then wait for the IP address that corresponds to this name. If the requested information is stored in the DNS server’s database, the server immediately transfers the answer to the browser. Otherwise, the server transfers a request to the DNS server of another domain, which can either process the request itself or transfer it to another DNS server. All the DNS servers are integrated in the hierarchical structure according to the domain hierarchy of the Internet. A client (browser) interrogates these name servers until it finds the necessary correspondence. The DNS database has a tree structure called a domain area of names, in which each domain (a node of the tree) has a name and can contain sub-domains. The name of a domain identifies its position in this database in relation to the parent domain, and points in the name separate parts corresponding to the domain nodes.