To address the network nodes of Internet, the special digital combinations are widely used. These digital combinations are called IP addresses. DNS (Domain Name Service) is used to perform conversions between alphanumeric character and numeric addresses. An IP address can usually be written using four numbers in the decimal system, for instance: or DNS allows you to match the IP address and domain name, for instance: =

DNS servers (that respond on the Internet to requests about your domain or zone) are required in order to provide a proper functionning of the domains. To improve the reliability of a domain, there must be at least two DNS servers. The server, where full primary information about the domain zone is stored, is called Primary DNS. All other servers, where information on this zone are called Secondary DNS.

Information about the domain (also known as the zone file) contains several different types of records.

The most important types of DNS records are the following:

  • – А record (address record) connects IP address with host name, where a site is located.
  • – NS record (name server record) points at the DNS server, where the records on this domain are located.
  • – CNAME record (canonical name record). This record is used to redirect requests form one domain to another.
  • – MX record (mail exchange record) points at the e-mail exchange server for the domain.
  • – SOA record (Start of Authority record). This record indicates that one of the DNS servers is Primary one; the record also contains contact information of the one responsible for this zone, timing of interaction between DNS servers and caсhing of information by the zone.
  • – SRV record(server selection record) points at servers addresses for different services. It is usually used for Jabber and Active Directory.