Hi everyone 👋

Let me say something that might be controversial in tech education circles.

The way the OSI model is normally taught is the reason most people never actually understand it.

You know the drill. Seven layers, memorise them in order, use a mnemonic like "Please Do Not Throw Sausage Pizza Away," answer the exam question, and forget the whole thing within a week. You technically "learned" it, but you could not explain what it actually does or why it exists.

In Post 3 of my Networking Foundations series, I set out to fix that by teaching it the opposite way.

Here is the core idea: if you have followed the series so far, you already understand the hard part. You have already met packets, headers, encapsulation, IP addresses, and MAC addresses. The OSI model is simply the formal name for that structure. It is not new information to memorise. It is a label for something you already understand.

So the post does not ask you to memorise seven names. It teaches you seven jobs.

It covers:

→ Why the OSI model exists at all (the early networking world was a chaos of incompatible systems, and the industry needed a shared reference)
→ All seven layers explained as jobs, not names, each with its real-world protocols, devices, and data unit
→ The honest truth most tutorials skip: the internet does not actually run on OSI. It runs on the simpler four-layer TCP/IP model. The post includes a full side-by-side showing exactly how the two map together.
→ The security payoff that makes the whole model worth knowing

That last point is the one I care about most. When you understand the layers, you understand where in the stack any given attack operates, and therefore what kind of defence can possibly stop it.

A TCP SYN flood is a Layer 4 attack. No web application firewall (Layer 7) will stop it.

ARP poisoning is a Layer 2 attack. It happens below the level a traditional IP firewall even looks.

SQL injection is a Layer 7 attack. Your network firewall passes it happily, because to the network it looks like ordinary web traffic.

Match the defence to the layer, or it does nothing. That single skill, placing an attack on a layer and reasoning about the right defence, is worth more than any mnemonic.

The post includes four original diagrams: the full seven-layer stack, the encapsulation flow, a per-layer attack map, and the OSI vs TCP/IP comparison.

📖 Read Post 3 here: https://vickkykruzprogramming.dev/blog/the-osi-model-demystified-not-memorised

This is part of an ongoing 14-post series taking readers from the basics of networking through to Zero Trust security. Subscribe to our newsletter to get each new post as it publishes. 🔔

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