All language subtitles for 1. OSI Model The Beginning

Now let us talk about the oocyte model now the old model is nothing more than a model.

I mean that's really the best way to explain it.

So if I wanted to build an airplane

what I do I will build this interesting airplane model to give me an idea what the airplane might look

like.

If I was going to design something you're going to have to practice stuff like that.

But I have some type of model to have something of an idea of what it will look like.

This is similar to that not 100 percent but it's similar if I wanted to have these methods this way

of communicating between one device and another I would have some type of model to use to make sure

that communication happens between one PC or another

so although again this is something that we are not going to be changing we're not going to be going

in there and making changes.

Do these layers first say some of the configurations that we do will make changes to the to the actual

layers as the data is being sent out.

But this model is based on communication between one PC and another

we call this the other side model.

And as you can see it has seven layers.

The layers will start to make sense here.

By the time we're finish starting at the top we have application presentation and one session transport

network data link physical.

But at time you don't just CCN a training mission all of these by heart as far as the names of these

layers as far as understanding what each one of them does you should have a OK understanding of application

presentations and session you should have an ok understanding of transport love it more than OK understanding

I should say and network and data like you should have a pretty good understanding now and I mean understanding

you're going to understand how these layers are built.

And then oh I'm motto is use as a means of educating us on how this traffic is moving from one day to

another.

And so I wanted to build protocols at a particular you know and you know deep down and one to build

protocols or script from scratch manipulate protocols you know create a device that needed to run protocols

they would use a model like this.

These modeled each one of these models go pretty deep.

But as a CNA you're likely going Zanti but you could be going deeper now whereas not something new is

going to remember off the top of your head you will have to deal with some some headaches as far as

learning this information so let's talk about what these layers do.

Now remember we're talking about communication

so when we're sitting in traffic from PC want to

depending on what type of book depending on what type of data we're going to be grabbing we might not

use all the layers.

Well let's say we actually want to use all the layers for this particular application or to print this

particular transmission and PC was going to communicate with PC too.

And what he wants to get is some dado I will see web page Dedo So you go out and you say hey I'm going

to go to www.youtube.com

Now this information is going to be sent over to PC PCs and PC to says Let me give you that information.

So what I have to do is I'm going to send you this information and as I'm sending it to you I'm going

to build my layers one by one.

Before I send this traffic out so the application layer them the occasional error is really where the

user sets so if I was sitting on a web browser here this is where the user interact with the application.

Now when you start reading about each one of these layers it's a lot to them.

I'm just giving you the basics.

So use a sense down here use a particular application and that application will be communicating with

another device.

So in this application we use Firefox

web browser we're going to fire five for typing yahoo dot com see that the information over here and

p.s. to is going to be using some information that you sent back he's going to have a presentation layer

and that data that is presentation layer pretty much does what it says it's how the data needs to be

presented to the user.

Have you ever pulled up a web page and the data was like all in this format You know normally you know

this piece of data should be over here on the page in this box and this piece of data should be up here

at the head or somewhere.

You know this one should be a picture sitting over here you know but somehow the presentation information

didn't get sent over somehow the presentation layer got corrupted got messed up somewhere.

So we end up getting this type of format that's all in the left hand side all up and down and it doesn't

make any sense.

It's happened to me many times.

This is the presentation layer not being sent over to where it needs to get to somehow the presentation

layer did not either present the information correctly.

Or it just wasn't sent over so that other PC has received no information didn't know how to present

the data to the user.

Does that make sense.

So this presentation layer it's job is to make sure that the data is presented correctly.

Now you can look at the fact that I'm a user and I'm going to use this application the application is

going to send information to the presentation layer saying look this is how I want this to be resented

before sent out and then a presentation layer is going to actually look towards the session to create

a session between two pieces I'm going to talk about that in a minute.

Now I of the presentation is heavily relied on the session.

But each one of these layers works with each other.

They relied on each other to do their job so their job can be done.

Read about Dorsai model this is a reading topic.

There's lots of topics that the reading topic

session

it is the means of creating communication from one PC from another member we talked about the walkie

talkies and we talked about the channel well imagine these logical channels these logical pathways where

the data itself

we'll travel down those logical paths

this session is really important because when PCI-E transit PC one tries to communicate with P-T to

there needs to be some sense of communication p.s. one is going to send information over to PC to say

look I'm I'm I'm trying to communicate with you.

P.S. cool says OK I get that.

Let's go ahead and let's start a communication and it's a logical flow there's logical channel so to

speak between these two PCs.

Will be formed and then we'll start sending data between PC wanted PC to use in these logical channels

so to speak but these logical channels are called Sessions

now the job of the session layer it's job is to maintain

that session but in order to maintain it it has to one and has to start the session it's also a job.

After starting the Sassa and maintaining it its job is also to stop the session or tear it down.

When the communication between the two PCs is done that's his job that's the job of the session layer

of the assignment.

They're just logical connections between PC wanting to

now to transport layer pretty interesting the job of the transport layer it's a job is to communicate

using traffic that is called UDP

TCAP