TCP/IP Model
The TCP/IP Model is the practical networking model used by the Internet.
Unlike the OSI model, which has 7 conceptual layers, TCP/IP has 4 layers.
Application
Transport
Internet
Network Access
The TCP/IP model groups some OSI layers together to keep the practical model simpler.
1. Application Layer
The Application Layer contains protocols used directly by applications.
Examples:
- HTTP
- HTTPS
- DNS
- WebSocket
- SMTP
- FTP
It decides what the application wants to send.
Example:
GET /users HTTP/1.1
Host: api.example.com
This is application data.
2. Transport Layer
The Transport Layer decides how data should be delivered between applications.
Main protocols:
- TCP
- UDP
TCP is used when reliability matters.
UDP is used when speed and low latency matter more than guaranteed delivery.
This layer also uses ports.
Example:
Client → Server IP + Port 443
The IP address identifies the machine.
The port identifies the application or service on that machine.
3. Internet Layer
The Internet Layer handles addressing and routing across networks.
Main protocol:
- IP
It decides where the packet should go.
Example:
Source IP : 192.168.1.10
Destination IP : 142.250.xx.xx
Routers use destination IP addresses to forward packets.
4. Network Access Layer
The Network Access Layer sends data over the local physical network.
Examples:
- Ethernet
- Wi-Fi
- MAC addresses
It handles local delivery and physical transmission.
Example:
Your laptop may send data to your router using Wi-Fi. After that, the router forwards it toward the internet.
TCP/IP Model Summary
| TCP/IP Layer | Common Protocols / Concepts |
| Application | HTTP, HTTPS, DNS, WebSocket, SMTP, FTP |
| Transport | TCP, UDP, ports |
| Internet | IP, routing, ICMP |
| Network Access | Ethernet, Wi-Fi, MAC addresses, frames |
Example: Opening a Website
Suppose you open:
https://example.com/users
The flow looks like this:
Application Layer
Browser creates an HTTP request
↓
Transport Layer
TCP prepares reliable delivery
↓
Internet Layer
IP adds source and destination IP addresses
↓
Network Access Layer
Wi-Fi or Ethernet sends the frame over the local network
At the server, the reverse happens.
The server receives the data from the network, removes each layer's information, and finally the web server reads the HTTP request.
Interview Answer
If an interviewer asks:
Explain the TCP/IP model.
You can answer:
The TCP/IP model is the practical 4-layer model used by the Internet. Its layers are Application, Transport, Internet, and Network Access. Application contains protocols like HTTP and DNS. Transport uses TCP or UDP for application-to-application delivery. Internet uses IP for addressing and routing. Network Access handles local network delivery using technologies like Ethernet, Wi-Fi, and MAC addresses.