Only very, very loosely related to this. But can someone explain why we learn the OSI model, despite the fact that as far as I’m aware it’s completely theoretical and has never been used, but the TCP model is ubiquitous?
Once upon a time there were more protocols than just TCP/IP. You could have IPX/SPX, Baynes and others.
Hell. Even now with the introduction of Quic, it’s starting to change the use of TCP/IP, so having a general understanding of the layers in an abstracted manner let you map them to the different syntaxes that are out there. Kind of like programming languages.
We’ve also had UDP this whole time
Yup. Quic, for example, layers on UDP instead of TCP. It’s still an IP based protocol. But then you can also get things like FCoE which don’t even use TCP/UDP. Or even ATM which uses its own frame structure. There’s plenty of reasons to need to understand the OSI model.
What do you mean “Theoretical” and “Never been used”? Are you writing this by sending off radio waves purely with your mind? Am I the only one using a modem and computer? (/j, but it seems to me that you’re asking “why a plane needs engines and wings, when it already has a payload”)
TCP (and UDP) just describe how to assemble the data into packages which can be somewhat reliably reassembled on the other end.
While it does have an address stamped on top (IP), it doesn’t know how to get anywhere by itself. That’s where the bottom 3 OSI layers come in (the physical wires - or wireless spectra/wavelengths - the data is transmitted through, the specifications of how the embedded devices talk to each other over these wires, and how to discover other embedded or other devices on a network). I can very much assure you that the wires do exist and are indeed in use.
Contrary, the upper layers are more about keeping communication going once a connection has been established.
You’re confusing TCP (the specific protocol) with the TCP/IP model, which is an entirely different model to describe the network stack to the OSI model, and which can only loosely be mapped onto it.
Apologies, that’s my fault, I thought you wrote “TCP model(/protocol)” and not “TCP/IP model”, which are indeed two very different things.
I feel that the OSI model focuses more on the specific layers with their relations and physical/digital setup, while the TCP/IP model has more of a abstract and “high-level”-focus. I think both have their ups and downs, though I’m still confused what about OSI is “theoretical and has never been used”.
No, you read it right. I just assumed my meaning would be clearer than it apparently was. To me, the word “TCP model” doesn’t strictly mean anything. There’s the TCP protocol, and the TCP/IP model. I assumed my usage of the word “model” would make it clear that I meant the latter, but I guess I can see how people would interpret it as the former.
though I’m still confused what about OSI is “theoretical and has never been used
A real-world implementation of OSI would involve separate protocols for each layer. There have been numerous different ways of describing TCP/IP in terms of OSI layers, but roughly speaking, the broadest possible interpretation is that TCP/IP’s “application layer” covers OSI layers 5, 6, and 7, with TCP covering layer 4, and IP layer 3. But some analyses also suggest TCP/UDP ports are a layer 5 concern. Ultimately, the TCP/IP networking model is a separate way of looking at things to the OSI model, and it would be silly to suggest that it’s the same.
Just saw this comment.
Yes, you are completely right. That’s likely also the reason for your confusion regarding OSI, since you appear to compare it to TCP/IP in a rather literal manner.
Obviously TCP/IP is better at describing TCP/IP than OSI, though while OSI also can be used to describe TCP/IP in a sub-optimal manner, TCP/IP cannot be used to describe OSI.
I can’t believe people are actually arguing with this guy. I gave up. Try asking him about frames and the media layer.
Not sure what the point of this kind of troll is.
No trolling. You “gave up” because you made a stupid comment saying that the TCP/IP model is an implementation of the OSI model. Which is a nonsense claim that any basic course on networking would disabuse you of.
Also no “arguing”. Everyone except you was having a very civil and engaging conversation.
If anyone’s “trolling” here, it’s you.
Side note: rule 2: be nice.
