TCP/IP Protocols & Layers

J277 Revision Master

Layer 4 (Top)

Application

Provides network services to applications. Formats data for user interaction.

HTTP / HTTPS
Hypertext Transfer Protocol. Used by browsers to access websites. HTTPS is encrypted.
FTP
File Transfer Protocol. Used for sending/receiving files across a network.
SMTP
Simple Mail Transfer Protocol. Used to send emails to a mail server.
POP
Post Office Protocol. Retrieves email; usually deletes it from the server once downloaded.
IMAP
Internet Message Access Protocol. Retrieves email; syncs across devices and keeps mail on server.
Layer 3

Transport

Manages data transfer. Breaks data into packets and ensures reliable arrival.

TCP
Transmission Control Protocol. Splits data into packets and checks for errors or missing data.
UDP
User Datagram Protocol. Fast but no error checking. Good for streaming or gaming.
Layer 2

Network

Routes packets between networks by adding source and destination IP addresses.

IP
Internet Protocol. Adds IP addresses to packets so they can be routed correctly across the internet.
Layer 1 (Bottom)

Link

Handles the physical transmission of data bits through hardware like cables or Wi-Fi.

Ethernet
Ethernet. Wired network hardware standard. Uses MAC addresses.
Wi-Fi (802.11)
Wi-Fi. Wireless standard using radio waves to transmit bits between devices.

Protocol Overview

Web: HTTP/HTTPS

Browsing websites. HTTPS adds encryption for security.

Files: FTP

Moving files between a client and server reliably.

Reliability: TCP vs UDP

TCP checks for errors (Web/Email). UDP focuses on speed (Gaming/Calls).

Why use Layers?

Interoperability

Devices from different brands can communicate using standard rules.

Modularity

Developers can update one layer without affecting the others.

Troubleshooting

It's easier to pinpoint exactly where a network fault has occurred.