DNS is a system of servers that store data of domain addresses. Thanks to the DNS servers, Internet users can use the web addresses in the form which is easy to assimilate (composed of letters and digits). DNS “translates” them into a string recognized by the network, i.e. the string of numbers. For example, the domain google.com is “translated” to 220.127.116.11. DNS is also a communication protocol that describes the method of connection clients to DNS servers.
DNS is a complex computer system and the legal system. It provides on the one hand the registration of Internet domain names and their associated IP numbers. On the other hand, performs ongoing maintenance of PCs find their IP addresses corresponding to the various appellations. It is essential of the operation of almost all Internet services. Domain names can contain letters, numbers and the character ‘-‘. DNS as an organizational system consists of two institutions – the IANA and ICANN. They monitor the general rules for the granting of domain names and IP addresses. But they do not deal with individual domains they are willing allocation, only separate top-level domain.
The technical basis for the DNS is a global network of servers that store information about domain addresses. Each entry contains a name and corresponding value, usually the IP address. DNS is the basis for resolving host names on the Internet. DNS is also a communication protocol to connect to customers’ DNS servers. Part of the protocol specification is also a set of recommendations on how to update the entries in the databases of Internet domains. In the world there are many DNS servers that are responsible for handling specific Internet domains. Domains have a tree-like structure on top is the 13 root servers (root servers) that support top-level domain (TLD – Top Level Domains).
DNS is based on 13 main servers called in English the root-servers, having the name of a.root-servers.net to m.root-servers.net. There may be more, limitation stems from the fact that a single UDP packet with a standard size of 1500 bytes is located just about up to 13 servers. DNS queries and replies are usually transported in UDP packets. Each message must include in a single UDP packet (typically 512 octets, but this figure can be changed also remember to set the same size of MTU – Maximum Transmission Unit). In the other case is sent to TCP and preceded by a two-byte value indicating the length of the question and the answer length (not including the two bytes).