The TCP/IP Model Explained — 4 Layers, Real Examples
The TCP/IP model is the 4-layer framework the real internet runs on: Application, Transport, Internet and Network Access. It's a simpler, practical cousin of the 7-layer OSI model — engineers use OSI for precise troubleshooting vocabulary and TCP/IP for how things actually work.
The 4 layers and their jobs
| Layer | Job | Examples |
|---|---|---|
| Application | User-facing protocols | HTTP, DNS, SMTP, FTP |
| Transport | End-to-end delivery, ports | TCP, UDP |
| Internet | Logical addressing & routing | IP, ICMP |
| Network Access | Physical delivery on the link | Ethernet, Wi-Fi, ARP |
How OSI maps to TCP/IP
OSI's top three layers (Application, Presentation, Session) collapse into TCP/IP's single Application layer. OSI's Physical and Data Link merge into TCP/IP's Network Access. Transport and Internet map one-to-one (to OSI's Transport and Network). Knowing both is expected at CCNA — see the full OSI model guide.
Frequently asked questions
What are the 4 layers of the TCP/IP model?
Application, Transport, Internet and Network Access — from the software you use down to the physical link that carries the bits.
What is the difference between TCP/IP and OSI?
OSI is a 7-layer conceptual reference; TCP/IP is the 4-layer model the internet actually uses. OSI's top three layers map to TCP/IP's Application layer.
Which model is used in real networks?
TCP/IP — it's what every internet-connected device runs. OSI is used mainly as a teaching and troubleshooting reference.
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