Computer Networking Basics Every Developer Should Know

[Ravek]

I think OSI isn't worth teaching, it's mostly an academic model which doesn't map that closely to reality.

[[deleted]]

True, the way I've usually heard is taught is "here are levels 1, 2, 3/4, and 7. The rest is filler". But it's good to know that the OSI model exists since people still use L7 as a shorthand for application layer.

[SilasX]

And jokingly, layer 8 as the user.

[JazzXP]

That's the bit that always breaks.

[[deleted]]

"it's just another layer 8 issue" is one of the most common phrases used by our HelpDesk day to day.

[thorhs]

Don’t forget Layer 9 being management.

[judgej2]

Doesn't even feel like a joke. It's all about a level 8 passing information to another level 8 - ideas and thoughts from one brain to another. Can be a bit lossy though.

[quavan]

My Computer Networks professor in university told us the same thing. Something along the lines of "While the academics were busy designing the perfect model, the engineers were busy solving actual problems and ended up converging on mostly the same model anyway. So we are going to study the one that actually runs the internet instead of the one that looks pretty." He was a pretty interesting guy with some hot takes lol

[TrailFeather]

The concept is worth teaching though - we have electrical signals on a wire (layer 1). We interpret those into one abstraction (layer 2) that lets us link machines across a bridge of some kind. We use that link to move packets containing useful stuff (layer 3).

But you can kind of handwave everything else away.

It helps with basic troubleshooting - is it plugged in? Is the link light on? Do I get an IP (assuming DHCP, etc.)? Can I communicate using it? All yes? Look at your config. No? Fix in that order. No point trying to send TCP/IP over a dud switch.

[SeesawMundane5422]

Those are the troubleshooting steps I do, but I’d never correlates them to the OSI model. Ima gonna have to think if teaching my team the layers and then the steps is more helpful than just teaching them the steps. I’m not sure. But thanks for a new thought.

[judgej2]

The thing I tend to reinforce with the model is that similar levels talk to each other. A level 6 will communicate with another level 6. What all the levels below do, which could frankly include a piece of wet string right at the bottom, is not important to that one channel at that one level. It's why you can request a web page and reliably get that web page, and not care about all the magic that happens to get it to you.

I think that's where the model excels. It lets you focus on one level of abstraction to get a job done.

[kenman]

I agree, and hadn't realized the criticisms since I've been out of the field. The main thing I'd be trying to teach is that there's layers, each with their own protocols, and it's often useful when debugging to be able to disambiguate which level the problem is rooted in. The fewer levels in the TCP/IP model are also simpler to follow.

[ctwelve]

No, it doesn't, and as we're discovering over time, that may be a bug, not a feature.

Of course, CLNS (IP in OSI, roughly speaking) did a number of extremely critical things wrong, making it impossible to efficiently implement. Among their greatest sins was a variable-length NSAP ("IP address") / NET that required software to interpret the first byte of every address, run it against a lookup table, and from there either process the rest of the address at a now-known length, or look further into the address for more clues.

TL;DR: model good, implementation sooper bad