now, lastly, we have our layer seven. We have our application layer. Now. Our application layer is going to be our next network access layer. It's going to be what enables our applications to access the network. It does things like identify communications Partners that identifies who were trying to connect to
it determines our resource availability, such as our network availability for these applications using the network,
and it helps to synchronize our communications. Now when we're talking about our application layer, we're talking about protocols such as SMTP for when we're sending email. We're talking about http for resolving are taking Web pages and opening up a Web pages and browsing the Internet
or FTP file transfer protocol.
So our application layer is really going to be the layer that are is working on our computer, where our applications are installed. Software operating system is determining
how it can access if these applications can access the network. In the case of http, this is where our browser is trying to determine if it can establish a network connection if it wants. If it needs to connect to this Web server where this Web server is,
and it also determines our network resource is
if we're able to connect to this or how much resource is how many? How much network usage I can put into Take opening your loading this Web page through our layers one through six. So far, we've established a physical connection. We've established a data link connection. We've, uh,
taken an I P address and we've gotten an I P. Address and we've
sent network data through our we've sent data over the network using routers, Another layer three devices. We've established our TCP or UDP for transporting our day of data on our layer four.
We have our layer five our session layer. We've established what kind of protocols were using. We've We've created a handshake with whoever we're trying to talk. Thio, layer six. Our presentation later, we've encrypted or we we've started encrypting the data that we have on our application layer is going to be what takes that data
and we're gonna really start using it with our applications. We're going to create, we're gonna take it,
and we're going to use it in a way that we can now see it on our screen. Our application layers want to take the data and put in an application or take our application and allow it to transfer data.
Now that we're the end were at our layer seven.
We can also see how are OS I model sort of goes up and down the chain.
What I mean by that is if we have
a computer here that sending to another computer
we're really not just going down. Roos I model once, we're really going down at once and then going back the other way. So if we start on our computer A here to our computer B and we're running over, say f c p or we are a secure file transfer protocol,
and we are trying to take a file, and we're trying to send it to computer. Be
what we're now. We're starting at the application layer.
So our computer is trying to determine how much resource is it has in order to take this file and get it ready to send is trying to determine if we have network connectivity. And if we're able to access the network in order to send this file, these are gonna be our layer seven at our application layers on our first computer.
So we're getting ready. We're getting this file ready to send
on. We're trying to determine if we have that network access. Then we have a presentation later. Maybe we're taking this file and we're encrypting it. That's our layer six. So we now gone down the next layer. The Slayer's been this lady's been taken has been encrypted, and so we now have it ready to go.
Then we have our session layer. Our computer now attempts to establish some sort of handshake with the other computer it's going to manage, manage The connection is going to get the connection ready to go.
Then we have a transport layer transport layers going to decide how it's gonna transport this over TCP or UDP. Since this is an encrypted file and we want to make sure that all of our packets get there, we're gonna use TCP and we're going to have that receipt. And when the other side are computer be receives, the file is going to send us back a return return on delivery.
When we have our layer three, our network layer Both of our computers here have I P addresses we're gonna have to be sending this packet. We're gonna have to be sending this connection over the network through different routers.
Then we have our data link layer our computer. Now that has his I p address that I p addresses logically assigned to. It's, too. It's Mac address. And so that Mac address is in charge of managing that, managing where that I P address is assigned to physically
so that it can again send out that data properly.
And then, lastly, we have our physical layer. Now that we have gotten our application, our application has determined our resource is, and it's allowed our application to talk to our network. We've encrypted that file. We've started a session or we've taken the steps necessary in order to get ready to create a session
gotten ready to manage TCP or UDP. We have our I p address. We have our Mac address, and now we're going. We have that data and it's down into our small bits, and it's ready to send as electrical impulses across our cable.
And then all of that occurs sending
across our network and then our computer be also performs. All of those functions, but sort of in the opposite manage manner. It receives the physical, the physical impulses to its Mac address, and it's using it, and it's using I P networking, and it has TCP or UDP, and we're messing. We're managing the session and what's going on
if we've established a connection or for terminating the session,
we were decrypting the file. We're decrypting the data, and then our application, which is receiving that file, which is receiving that FTP transfer transfer, is now receiving. The applicant is now receiving the file and is now taking it. And then using our network resource is so
we can see how, at any given point in our network connection,
we're really we're really using. All seven layers of our OS I model are different layers, maybe more prevalent at certain times, such as when we're rounding data through our through a router. When we're thinking of a router, we're thinking we were talking about a layer three object
because it's going to route data
or when we're talking about a cable on electrical signals. We're talking about layer one. We're talking about our physical layer, but we need to understand how our Os I'm model plays into all of all of our networking capabilities and how to understand Roos I model and break up these different layers
so that we can better understand what's going on when we're transferring and receiving data.