What are DNS? - Complete Guide
What are DNS? - Complete Guide
The Domain Name System (DNS) is a fundamental Internet infrastructure that acts as a digital "phone book". Its main function is to translate domain names that we easily remember (like google.com) into the numerical IP addresses that computers need to communicate with each other.
Complete Technical Definition
DNS is a hierarchical decentralized naming system for devices connected to IP networks like the Internet or a private network.
The DNS server uses a distributed and hierarchical database that stores information associated with domain names on networks like the Internet.
How Do DNS Work?
When you type a URL in your browser, a complex DNS resolution process occurs involving multiple levels:
Local Query (DNS Cache)
Your device checks its local DNS cache to see if it already knows the domain's IP.
Recursive DNS Server
If not in cache, the query is sent to the configured recursive DNS server.
Root Servers
The recursive server queries the 13 global Root Server clusters.
TLD Servers
Root Servers redirect to Top Level Domain servers (.com, .es, .org).
Authoritative Server
The specific domain's authoritative DNS server is queried.
Response and Cache
The response is returned and each server caches info according to TTL.
Main DNS Record Types
A Maps a name to an IPv4 address
example.com → 192.168.1.1
AAAA Maps a name to an IPv6 address
example.com → 2001:db8::1
CNAME Alias from one name to another
www.example.com → example.com
MX Specifies mail servers
example.com → mail.example.com
TXT Arbitrary text information
SPF, DKIM, verifications
NS Specifies authoritative name servers
example.com → ns1.provider.com
Main DNS Record Types
A Maps a name to an IPv4 address
example.com → 192.168.1.1
AAAA Maps a name to an IPv6 address
example.com → 2001:db8::1
CNAME Alias from one name to another
www.example.com → example.com
MX Specifies mail servers
example.com → mail.example.com
TXT Arbitrary text information
SPF, DKIM, verifications
NS Specifies authoritative name servers
example.com → ns1.provider.com
SOA Start of authority for a DNS zone
Zone administrative information
PTR Reverse resolution from IP to name
1.1.168.192.in-addr.arpa → host.example.com
SRV Service addressing
_sip._tcp.example.com → sip.example.com:5060
CAA Certificate authority authorization
example.com → letsencrypt.org
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