TCP/IP Model vs. OSI: How the Internet Actually Works

Laster week, we climbed the 7-layer mountain of the OSI Model. While that model is great for learning, it’s mostly theoretical. In the real world. Your computer will use the TCP/IP Model (also known as the DoD Model)

Today, we’re breaking down why this model won the “Protocol War” and how it simplifies the 7 layers into 4

1. The Four Layers of TCP/IP

The TCP/IP model is more efficient because it groups function together absed on how software actually handles data.

TCP/IP Layer	OSI Equivalent	What Happens Here?
Application	Layers 5,6,7	Handles the UI, Data formatting, and session control.
Transport	Layer 4	Manages host-to-host communication (TCP/UDP)
Internet	Layer 3	Routes packets across networks (IP)
Network Access	Layer 1,2	Handles the physical wires and MAC addressing.

Breaking Down the Stack

Layer 4: Application

In the OSI model, we spent three days talking about Sessions, Presentation, and Applications. In the TCP/IP world, this is all one big layer. If you are using HTTPS, SSH, or DNS, You are working at the Application layer. It handles the data and the encryption all in one go.

Layer 3: Transport

This maps exactly to OSI Layer 4. It’s responsible for the “End-to-End” Delivery. This is where the TCP Three-Way Handshake happens and where Port Numbers (Like 80 or 443) are assigned to keep different conversations separate.

Layer 2: Internet

This maps to OSI Layer 3. Its only job is to get a packet from point A to point B across different networks. It doesn’t care about the hardware; it only cares about the IP Address.

• Key Protocols: IPv4, IPv6, ICMP

Layer 1: Network Acess

This is the “Hardware” layer. combining OSI Layers 1 and 2. It deals with how bits are physically put onto the wire (Ethernet, Wi-Fi) and the hardware addresses (MAC addresses) that get data to the next local hop.

3. Why Did TCP/IP Win?

You might wonder why we even bother with the OSI model if the internet uses TCP/IP

• OSI was designed by a committee to be a perfect, universal standard.
• TCP/IP was designed by the Department of Defense (ARPANET) to be Resilient and Functional.

TCP/IP won because it was simpler and it was implemented first. IT’s “Leaner” it doesn’t have the overhead of strictly separating things like “Session” and “Presentation” when most modern apps do those things simultaneously.

4. The “Support Associate” Practical View

When you’re troubleshooting at your job, you’ll often find yourself using “TCP/IP” logic without realizing it.

• If you run ipconfig, you’re checking the Internet Layer.
• If you check if a website is up via https://, you’re at the Application Layer.
• If you check the link light on a switch, you’re at the Network Access Layer.

What’s Next?

Now that we understand the “Models,” we need to learn how to speak the language of the internet Layer. Tomorrow, we will start the most feared but important topics in IT: IP Addressing and Subnetting. Don’t worry, I will try to break it down so simple that we will all be able to do it in our heads.