Network

Layer Number
ISO OSI Model
TCP/IP Model (RFC 1122)
Protocols
Main Function

7

Application Layer

Application Layer

HTTP, HTTPS, FTP, POP3, SMTP, IMAP, Telnet, SSH,

Providing services and interfaces to applications

6

Presentation Layer

Unicode, MIME, JPEG, PNG, MPEG

Data encoding, encryption, and compression

5

Session Layer

NFS, RPC

Establishing, maintaining, and synchronising sessions

4

Transport Layer

Transport Layer

TCP, UDP

End-to-end communication and data segmentation

3

Network Layer

Internet Layer

IP, ICMP, IPSec

Logical addressing and routing between networks

2

Data Link Layer

Link Layer

Ethernet 802.3, WiFi 802.11

Reliable data transfer between adjacent nodes

1

Physical Layer

Electrical, optical, and wireless signals

Physical data transmission media

DNS record type

DNS Record

Description

A Record

Holds the IPv4 address of a domain.

AAAA Record

Contains the IPv6 address of a domain.

CNAME Record

Forwards one domain or subdomain to another domain but does not provide an IP address.

MX Record

Directs email to an email server.

TXT Record

Allows admins to store text notes in the record, often used for email security.

NS Record

Stores the name server for a DNS entry.

SOA Record

Stores administrative information about a domain.

SRV Record

Specifies a port for specific services.

PTR Record

Provides a domain name in reverse DNS lookups.

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