Domain Name System

This post explains briefly what is a domain name system (DNS).

FAQs about a Domain Name System

What is a Domain Name System (DNS)?

A domain name system (DNS) is a hierarchical and distributed naming system for computers, services, and other resources in the internet.

A DNS, basically, translates a domain (e.g. into an IP address (e.g. 123.456.789.123). DNS allows that users handle the more human-friendly alphanumerical characters of a domain rather than sets of the more difficult to remember numbers of an IP address.

What is a name server?

The Domain Name System is maintained by a hierarchical and distributed database system, which uses the client–server model. The nodes of this database are the name servers. The top of the hierarchy is served by the root name servers.

Each domain has at least one authoritative DNS server that publishes information about that domain and the name servers of any domains subordinate to it. This is why whenever you register a name, you need to define a DNS server.

What type of records are stored within a DNS?

The records stored in a DNS are called resource records (RR).

Type of resource records:

  • IP Address (A)
  • IP Adress (AAAA)
  • Domain Name Aliases (CNAME)
  • SRV
  • TXT
  • MX
  • A + Dynamec DNS
  • AAAA
  • CAA
  • NS
  • URL
  • Start of Authority (SOA)
  • Reverse DNS lookups (PTR)

A record is also know as host record. This record assigns a host name to an IP address. It is the most common record type in forward lookup zones.

CNAME record, also known as canonical name record, assigns a hostname to another hostname, that is called an alias. It is used for performs redirections.

SRV record is also know as service record. It is used to locate domain controllers and global catalog servers.

MX record, also known as mail exchange are used to locate the mail servers responsible for a domain.

Which fields have a resource record?

The resource record has these fields:

  1. Name of the requested resource (NAME)
  2. Type of RR (TYPE)
  3. Class Code (CLASS)
  4. Count of seconds that the RR stays valid (TTL)

What is the information contained in a record request?

When the info is requested, the question record contain this info:

  1. Name of the requested resource (NAME)
  2. Type of RR (TYPE)
  3. Class Code (CLASS)

How is the DNS info stored?

The DNS database is traditionally stored in a structured text file, the zone file, but other database systems are common.

DNS Security

You can find more information about DNS security on this post.

External references

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