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DNS | 53

                 +-----------+
                 |     .     |  ←----------------------|## Root Level [ . ] 
                 +-----------+
                       |
    +------------+------------+------------+
    |            |            |            | 
 +-------+   +-------+     +------+     +------+
 |  com. |   |  org. |     | net. |     |  lk. |  ←----|## TLDs [Top-Level Domains]
 +-------+   +-------+     +------+     +------+
     |                                      
 +------------------+
 |   h4rithd.com.   |  ←-------------------------------|## Second-Level Domain [SLD]
 +------------------+
          |
 +-------------------+
 | docs.h4rithd.com. |  ←------------------------------|## Subdomain [Third-Level]
 +-------------------+
          |
+---------------------------+
| staging.docs.h4rithd.com. |  ←-----------------------|## Hosts
+---------------------------+
                                               FQDN: docs.h4rithd.com
                                                     └──┘ └─────┘ └─┘
                                                  Subdomain SLD   TLD

### ROOT  →  The invisible Root of the domain hierarchy. (managed by ICANN)
### TLDs  →  Top-Level Domains. Commercial domain space (like .com, .org)
### SLDs  →  Second-Level Domains (your main domain name)
### Subs  →  Subdomains. Used to separate services like docs, blog, etc
### FQDN  →  The full Fully Qualified Domain Name
Type
Name
Description

A

Address Record

Maps a domain to an IPv4 address.

AAAA

IPv6 Address Record

Maps a domain to an IPv6 address.

CNAME

Canonical Name Record

Alias of one domain to another.

MX

Mail Exchange Record

Routes email to the correct mail server.

NS

Name Server Record

Specifies authoritative name servers.

TXT

Text Record

Arbitrary text, often used for SPF, DKIM, verification.

SOA

Start of Authority

Provides zone info: primary NS, contact, serial

PTR

Pointer Record

Used for reverse DNS lookups (IP → domain).

SRV

Service Locator

Defines location of services (used in VoIP, AD, etc.).

SPF

Sender Policy Framework

Helps fight spam by specifying allowed mail servers

CAA

Certification Authority Auth

Specifies which CAs can issue certs for the domain.

NAPTR

Naming Authority Pointer

Used for dynamic DNS, SIP, ENUM services.

RP

Responsible Person

Email address of the domain admin.

AFSDB

Andrew File System DB

Used for locating AFS or DCE services.

HINFO

Host Info Record

Specifies hardware & OS of a host (rarely used).

ISDN

ISDN Address Record

Maps domain to an ISDN number (obsolete).

KEY

Public Key Record

Used in DNSSEC (obsolete, replaced by DNSKEY).

DNSKEY

DNSSEC Public Key

Holds a public key for DNSSEC validation.

RRSIG

Resource Record Signature

Contains digital signature for DNSSEC data.

NSEC

Next Secure Record

Part of DNSSEC, lists next valid record.

NSEC3

Next Secure Record v3

Secure denial of existence (hash-based).

DS

Delegation Signer

Indicates that child zone is secured with DNSSEC.

LOC

Location Record

Specifies geographic location (lat/lon/altitude).

DNAME

Delegation Name Record

Like CNAME but for an entire subtree.

TLSA

TLS Authentication Record

Used in DANE to specify TLS certs.

SSHFP

SSH Public Key Fingerprint

Stores SSH key fingerprints for trust.

SVCB

Service Binding Record

New alternative to SRV for HTTPS/SVC discovery.

HTTPS

HTTPS Service Record

A variant of SVCB optimized for HTTPS.

URI

Uniform Resource Identifier

Maps domain to a URI.

MB

Mailbox Domain Name

Maps domain to a mailbox host (obsolete).

MG

Mail Group Member

Identifies members of a mail group (obsolete).

MR

Mail Rename Domain

Renames a mailbox (obsolete).

MINFO

Mailbox Info

Info about mailbox or mail list (obsolete).

WKS

Well-Known Service

Maps service name to IP/port (obsolete).

X25

X.25 Address Record

Maps to X.25 network address (obsolete).

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