Welcome back to OpsSecurely! Today, we’re kicking off our eBPF series , but before we dive into that magical world of extended Berkeley Packet Filters, let’s take a moment to refresh one of the foundational concepts of networking: the OSI model.

What’s the OSI Model, Anyway?

Ah, the good old OSI (Open Systems Interconnection) model. It’s one of those things you learn when starting in networking, and while it may feel a bit dated, it’s still super relevant when it comes to understanding how networks function. Whether you’re troubleshooting, securing your infrastructure, or setting up some next-gen tech like eBPF, the OSI model is your go-to guide for figuring out how data travels through the network.

Breaking Down the Layers

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Here’s a quick recap of the 7 layers of the OSI model, from top to bottom:

1. Layer 7: Application Where it all begins. This is where applications like your web browser, email client, or even a DevOps tool interact with the network.
2. Layer 6: Presentation The translator. It handles data formatting, encryption, and compression, making sure that the data can be read by the application.
3. Layer 5: Session This layer establishes, manages, and terminates connections. Think of it as the traffic cop ensuring that conversations between devices are managed smoothly.
4. Layer 4: Transport Here’s where things like TCP and UDP come into play. It ensures reliable delivery (or unreliable, depending on your protocol) of data between systems.
5. Layer 3: Network The router’s playground. This layer handles IP addressing and routing, ensuring that data packets make it to their destination, no matter where that is in the world.
6. Layer 2: Data Link Ethernet lives here. The data link layer manages the physical addressing (MAC addresses) and makes sure data is transferred between devices in a local network.
7. Layer 1: Physical Wires, fibers, radios. This is the actual physical hardware that moves bits and bytes across your network.

Why Does the OSI Model Matter for eBPF?

You’re probably thinking, “Okay, cool, but what does this have to do with eBPF?” Well, understanding how data flows through the network is essential when working with eBPF because eBPF operates at multiple layers of the OSI model. Whether you’re looking to inspect packets at the network layer or improve security at the application layer, the OSI model helps you pinpoint where you need to focus.

eBPF interacts at several layers (especially layers 3 and 4), giving you unprecedented visibility and control over the traffic flowing through your system. So yeah, the OSI model isn’t just a relic from the past—it’s your guide to the future of networking!

The OSI Model in Action

Let’s say you’re monitoring network traffic or creating security policies with Cilium eBPF (spoiler: we’ll dive into this in future posts). You’ll need to understand what layer you’re interacting with to apply the right policies or get the right data. Whether you’re filtering IP packets at the network layer or managing TCP connections at the transport layer, your OSI knowledge will guide you through.

Stay tuned for our next post where we’ll jump into the exciting world of eBPF and see how it fits into this whole networking puzzle. Until then, keep exploring the layers—there’s always more to uncover!

Join us at OpsSecurely as we continue to geek out on DevOps, one post at a time. Got any burning questions or cool DevOps tips? Drop them in the comments—we’re all about sharing and learning together!

Derryn Edwards

Derryn Edwards is a self-taught tech enthusiast with over 11 years of experience in cloud infrastructure, DevOps, and cybersecurity. Passionate about automation and emerging technologies, Derryn loves geeking out on new tools and sharing knowledge through mentoring. When he’s not diving into code or infrastructure, you’ll find him exploring the latest trends in tech and helping others along the way.

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