O que é o DNS?
Existem três siglas que correspondem ao DNS. Eles tendem a ser usados de forma intercambiável, mas na verdade têm significados diferentes.
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D omain N e S sistema.
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D N N S erver
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D omain N ame S erviço.
Sistema de nomes de domínio
O Sistema de Nomes de Domínio fornece um serviço de diretório distribuído em todo o mundo .
Ele faz isso usando uma rede de Servidores de nome de domínio .
The Domain Name System (DNS) is a hierarchical decentralized naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities. Most prominently, it translates more readily memorized domain names to the numerical IP addresses needed for the purpose of locating and identifying computer services and devices with the underlying network protocols. By providing a worldwide, distributed directory service, the Domain Name System is an essential component of the functionality of the Internet, and has been in use since the 1980s.
The Domain Name System delegates the responsibility of assigning domain names and mapping those names to Internet resources by designating authoritative name servers for each domain. Network administrators may delegate authority over sub-domains of their allocated name space to other name servers. This mechanism provides distributed and fault tolerant service and was designed to avoid a single large central database.
Fonte Sistema de nomes de domínio
Servidor de nome de domínio
Este é um servidor que executa um serviço de nomes de domínio . O servidor pode estar executando todos os tipos de outros serviços também.
O serviço que um servidor de nome de domínio fornece pode ser considerado como um serviço de pesquisa de diretório , pois ele mantém um diretório de nomes de domínio.
Dado um nome, o Servidor de Nomes de Domínio pode retornar o endereço IP correspondente ao nome (supondo que haja uma entrada correspondente no Diretório).
Domain Name Servers (DNS) are the Internet's equivalent of a phone book. They maintain a directory of domain names and translate them to Internet Protocol (IP) addresses.
This is necessary because, although domain names are easy for people to remember, computers or machines, access websites based on IP addresses.
Information from all the domain name servers across the Internet are gathered together and housed at the Central Registry. Host companies and Internet Service Providers interact with the Central Registry on a regular schedule to get updated DNS information.
When you type in a web address, e.g., www.jimsbikes.com, your Internet Service Provider views the DNS associated with the domain name, translates it into a machine friendly IP address (for example 216.168.224.70 is the IP for jimsbikes.com) and directs your Internet connection to the correct website.
After you register a new domain name or when you update the DNS servers on your domain name, it usually takes about 12-36 hours for the domain name servers world-wide to be updated and able to access the information. This 36-hour period is referred to as propagation.
Fonte O que é um Servidor de nomes de domínio (DNS) e como funciona
Serviço de nomes de domínio
O Serviço de Nomes de Domínio é um serviço executado na porta 53 em um Servidor de Nomes de Domínio .
Esta porta é para onde uma solicitação é enviada para resolver um nome para um endereço IP.
During DNS resolution, DNS messages are sent from DNS clients to DNS servers or between DNS servers. Messages are sent over UDP and DNS servers bind to UDP port 53. When the message length exceeds the default message size for a User Datagram Protocol (UDP) datagram (512 octets), the first response to the message is sent with as much data as the UDP datagram will allow, and then the DNS server sets a flag indicating a truncated response. The message sender can then choose to reissue the request to the DNS server using TCP (over TCP port 53). The benefit of this approach is that it takes advantage of the performance of UDP but also has a backup failover solution for longer queries.
In general, all DNS queries are sent from a high-numbered source port (49152 or above) to destination port 53, and responses are sent from source port 53 to a high-numbered destination port.