Of what the service of DNS consists?
Domain Name System
The Domain Name System (DNS) is and hierarchic a distributed database that stores information associated to names of domain in networks as Internet. Although as data base the DNS is able to associate different types from information from each name, the most common uses are the allocation of names of domain to directions IP and the location of the servers of e-mail of each domain.
The allocation of names to directions IP is certainly the most well-known function of protocols DNS. For example, if direction IP of site FTP of reliable-hosts.com is 18.104.22.168, most people arrive at this equipment specifying ftp.reliable-hosts.com and not it direction IP. In addition to being easier to remember, the name is more trustworthy. The numerical direction could change for many reasons, without it must change the name.
Initially, the DNS was born from the necessity to easily remember the names of all the connected servers to Internet. At the beginning, SRI (now SRI International) lodged a called file HOSTS that contained all the well-known names of domain (technically, this file still exists - the majority of the present operating systems still can be formed to review their file hosts). The explosive growth of the network caused that the system of names centralized in file HOSTS would not be practical and in 1983, Paul Mockapetris published RFCs 882 and 883 defining what nowadays the modern DNS has evolved. (These RFCs have been obsolete by the publication in 1987 of RFCs 1034 and 1035).
For the practical operation of system DNS three main components are used:
* Clients DNS: A program client DNS who executes himself in the computer of the user and who generates requests DNS of resolution of names to a servant DNS (For example: What direction IP corresponds to nombre.dominio);
Understanding the parts of a domain name.
A domain name usually consists of two or more parts (technically labels), separated by points when it is written them in the form of text. For example, www.mahomedalid.org or es.Wikipedia.org
* To the label located to the right top-level domain is called to him more (English < Top Level Domain). As org in www.mahomedalid.org or es.Wikipedia.org
The DNS consists of a hierarchic set of servers DNS. Each domain or subdomain has one or more zones of authority than publish the information about the domain and the names of services of any domain including. The hierarchy of the zones of authority agrees with the hierarchy of the domains. At the beginning of that hierarchy one is the servers root: the servers who respond when he looks for to solve a domain of first and second level…
Types of servers DNS
Bind • PowerDNS • MaraDNS • djbdns • pdnsd • MyDNS • DNS (Windows 2000/2003)
Types of resolution of domain names
Two types of consultations exist that a client can make a servant DNS:
In the recursivas consultations the servant repeats the same basic process (to consult a remote servant and to follow any reference) until he obtains the answer to the question.
The iterative consultations, or iterative resolution, consists of the best answer than the servant of names can give. The servant of names consults his local data (including its cache) looking for the asked for data.
When it exists more of an authoritarian servant for a zone, BIND uses the smaller value in the metric RTT (Round-Trip Time) to select the servant. The RTT is a measurement to determine how much a servant in responding a consultation takes.
The process of normal resolution occurs of the following way:
1. The servant To receives a recursiva consultation from client DNS.
* A = Address – (Direction) This registry is used to translate names of hosts to directions IP.