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OK, so now we're going to get into one of my favorite topics always on.

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It all the way is because we understand how these players work, everything else they play.

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So in order to understand the application first, you first need to take a step back and get a grip

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on the policy.

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A lot of the generals.

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Right.

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What is the oversight?

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Well, we've all heard of it.

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You know, we hear about it in theory, but what exactly is it and why was it needed all those things?

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Right.

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So, Olesya.

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Right.

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So this is the open systems interconnection model.

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All right, so I think one of the best ways to understand this is to give you an example, right?

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So let's say.

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You are at a computer right here, that's you and what's up, and you want to connect to a Web server

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over here.

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You want to connect to that Web server.

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There's a couple of things that happen, right?

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Doesn't just happen automatically.

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There's a couple of things that need to take place before this connection can actually be established.

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So we open a browser and you enter and you need to connect a Web server on the Internet.

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Even if you need to connect to an internal file server, a false server on your local area network,

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what happens versus the application layer gets to work.

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This is where the.

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Network where application was.

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OK, application network aware application lives at this later.

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All right, and so from there, the data is going to move down to another layer, right?

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And the second layer may have already guessed, but it's going to actually move down to the presentation

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layer.

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Yeah.

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Then Tatian.

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And we get to the presentation later, you know, this is where, you know, there's encryption or formatting

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or any translation, all that stuff gets done at this layer and then the data will continue to move

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down even further, right.

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Until it gets to the next layer, which you then have the session layer and essentially handles the

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discussions, I think, about being logged into a Web page.

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Now, there's a session in a website, right, so that, you know, when you click through multiple

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pages, the computer can tie together all those connections to a single user.

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Right.

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That's pretty much what a session is.

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Now, all of these things, all of them, all these things happen on one physical system.

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Write the application, the presentation, the session.

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This is on your computer does not leave your computer.

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That doesn't hit the network yet.

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OK, but after you get here, this is when things get kind of interesting.

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Let me go ahead and clear this out.

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Let's talk about what happens to the other layers, so then we have what's known as the transport layer

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transport and you can guess what happens at the transport layer, right?

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This is basically the layer that is responsible for the reliable or unreliable delivery of protocol

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data units known as segments at this layer.

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And it can track those messages up into segments.

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You can label them and reassemble them.

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That all takes place at this transport layer there.

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The data is continually sent.

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It's continues to traverse the network and ends up at the next there, which is the network layer.

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OK, this is the layer that most of us, I think are familiar with network.

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Because, you know, this is when we start to talk about IP addresses or source and destination IP addresses,

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all those things live at this layer.

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The next layer in our journey down the TCP IP protocol stack or even Ossi model, next layer is the

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datalink layer data link.

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And this is layer two and this is where everything is put into a nice, tidy envelope and it's sent

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over the network as a stream of ones and zeros, OK, because that's all data is right.

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It's just ones and zeros.

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And the transmission medium can be either the air.

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If it's Wi-Fi, it can be glass.

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If it's fiber optics, it could be copper if using Ethernet cable.

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Right.

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But, you know, that's pretty much how this works conceptually, that it goes down the stack.

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It flows all the way down.

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Right.

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And then on the other side in the server, it passes up.

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So to move up from the physical layer into the destinations data layer and then into the destination's

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network layer transport layer all the way up to the application layers.

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Right.

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The session, the presentation of the application until it finally gets to the application.

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Right.

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And then the same happens in reverse at the data sent back to the client.

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So that's pretty much how that works.

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The main thing you need to really know here is that this is just a model.

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And really what we're using in today's networks isn't the same model.

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We're using the.

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So, you know, just to kind of break this down a little bit more at the transport layer transport,

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what you have is a segment, the data is referred to as a segment that when you get to the network layer.

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Data is technically referred to as a packet.

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Another term package gets moved around a lot and people use it in their vernacular interchangeably with

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just data anywhere, but specifically you look at the RFID, if you look at how the TCP IP networks

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functioned, how they were designed, and that work layer is home to packets, just trying to be syntactically

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correct here.

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And then finally, we have a data link layer.

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You actually have a frame.

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OK, so the date actually changed its name as it moves down through the TCP IP stack.

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OK.

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And of course, when it hits the physical layer, it's just bits and bytes and zeros and ones that ons

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it.

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Right.

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But that's pretty much one thing I want you to know right there.

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Another thing that's really important, but I want you to know is that routers live.

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At the network, layer and routers move packets at layer three.

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That's where the writers live.

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And later to.

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You've got switches.

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OK, and switches move frames at layer two.

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So they make forward decisions based on the Destination Mac address and the frame compares the incoming

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Mac address to what's in its content addressable memory, S.A.M. content addressable.

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Memory and it can make a forwarding decision based on the destination Mac address and the data that's

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in the camp table at that given moment in time.

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Right.

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That's really all you need to know.

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The main thing that's really important is the application layer deals with network aware applications.

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Right.

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So Chrom, they'll be an application layer application.

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Microsoft Paint.

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That's not an application layer application because that layer, that application, isn't that where.

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Right.

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So that's the key point there.

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If you get that, you've got it.

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All right.

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You got what you need for this particular section.

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So the next one, we're actually going to dig into the transport protocol and dig a little bit deeper

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into segments and how these rates will rise in the next.