What is the OSI model used for in Computer Science

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I’ve read and seen videos on the OSI model and from what I remember it’s just a reference model for how you should develop a network in a computer but it’s not strict in that you should follow it exactly how it looks?

I could be misremembering but if I’m not then my question is why do we use it in the first place? Is it just a checklist of sorts to make sure we’re including the main parts?

Also as a follow up question, in networking I always see ports as in port (long number) I am always confused are these actual physical ports?

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Layers. That is the simplest way of putting it. Separation of duty is another way

Organizing the seperate function to work interoperability. It’s a framework designed to ensure that these functions work together.

You have seen Cloud break this apart a bit, or should I say delegate some of these functions (ie – Physical is now handled by AWS, etc)

The OSI Model classifies network traffic into “layers”. Each layer interacts with specific protocols. This is why a few years back you’d hear folks talking about a “layer 7 firewall” and such…. hope this helps start your down the path of knowledge!

>I could be misremembering but if I’m not then my question is why do we use it in the first place? Is it just a checklist of sorts to make sure we’re including the main parts?

Essentially, this is correct. The OSI model is a way to characterize and standardize what each layer of the data flow should do, without specifying what it looks like or how it’s put together.

>Also as a follow up question, in networking I always see ports as in port (long number) I am always confused are these actual physical ports?

No; the term “port” here refers to a purely logical thing — that is, it’s not a physical thing you can touch. Port numbers are used by computers to identify specific applications, so that they only watch for traffic that’s meant for them.

The OSI model is used to try and segment the complexity of a network transaction into distinct blocs of focus. You write software that uses the network, but you don’t need to develop a full networking stack for every piece of software you write because your main focus is handing things off to the next layer in the model where someone else has written something you can interface with. Their layers can then interface with other layers, which allows for a higher degree of interoperability. Your application doesn’t care if the network it goes across is copper or fiber or microwave or wifi, just like the network doesn’t care if your data is for a web application or a database transaction or a streaming video. Being able to visualize semi-distinct boundaries between the various functions necessary for transactions allows us to focus on what we’re good at and let someone else worry about the rest of it.

The model is there so that people build networks and applications in a comparable manner. There are other models – for people who are only focused on the network level and not on the application development, for instance, might be more inclined to apply the TCP/IP model.

TCP/IP ports are not physical ports. Physical ports would be defined in layer 0/layer 1, while TCP ports are in layer 4. The ports you’re talking about are logical segments of that further help the network understand what kind of data it’s passing – “Ah, this is web traffic so I’ll point it at the web server, and this is a DNS request so it goes to the DNS server, and this is an e-mail so it goes to the e-mail server.”

>I’ve read and seen videos on the OSI model and from what I remember it’s just a reference model for how you should develop a network in a computer but it’s not strict in that you should follow it exactly how it looks?

Yes that’s a fairly apt description. The thing with the OSI model is that basically any computer network will implement all the layers, but not necessarily as separate components. Often the boundary between layers is fuzzy, or a single protocol covers multiple layers.

>I could be misremembering but if I’m not then my question is why do we use it in the first place? Is it just a checklist of sorts to make sure we’re including the main parts?

That’s one way to use it, yes. You could also use the OSI model to categorise the different layers of a network, to group similar protocols/implementations together, to describe the layer at which something functions (eg. Layer 3 vs Layer 7 firewall), or use it as a guide to troubleshoot network issues and narrow down where a problem originates.

>Also as a follow up question, in networking I always see ports as in port (long number) I am always confused are these actual physical ports?

No, they are logical. Essentially they identify the software service on a machine that is communicating over the network connection. It’s a requirement to allowing more than one “network connection” per physical connection.