Layer Six, The Presentation Layer.
Now the presentation layer
is responsible for formatting your data
that's going to be exchanged
and securing the data with proper encryption.
So when you think about layer six,
there's a couple of keywords I want you to remember.
Data formatting and encryption.
Every time we talk about data formatting or encryption,
I want you to think about layer six,
the presentation layer inside the OSI model.
Now when I talk about data formatting, what is that?
Well, data is going to be formatted by a computer
so that it has compatibility
between different types of devices.
There are some common ones out there
that you may or may not have heard of.
The first one is ASCII, which stands for
the American Standard Code for Information Interchange.
Now, ASCII is basically text.
It's what says that the capital A
is represented by the number 65.
In the old days of computers, we had ASCII,
and it was an eight bit code
that would tell us exactly what that letter was
or that symbol,
and ASCII characters do that for us.
For instance, ASCII character 40
is the @ sign for your email.
Then we have things like gifs, which are little pictures
that dance around and do motion,
or we have a JPEG file, which is used for photographs
or a PNG, which is used for images on the internet.
All of these are different types of data formats,
and based on that format, the computer knows
how to represent it on the screen
as it passes those files around.
Because at the end of the day,
all of these file formats really come down
to a series of ones and zeros on your computer's hard drive
or on your network.
Now when we talk about ASCII,
it really is just a text-based language for us to use.
This is going to ensure that the data is readable
by the receiving system
because now we're all speaking the exact same language
because ASCII isn't the only text-based language out there.
There's Unicode and a series of other ones.
But if we all use ASCII for instance, that means we all know
what the proper data structure is for it
and the proper formatting.
This allows us to negotiate data transfer syntax
for our layer seven at the application layer,
and we're going to talk about that in the next lesson.
Now the next piece of this layer,
of layer six is encryption.
This is another thing that the presentation layer
is going to be all about in doing for us.
Encryption is used to scramble data as it goes in transit
to keep it secure from any prying eyes.
This is going to provide us with confidentiality of our data
as it crosses our network and as it's stored.
Now some examples of this will be something like TLS,
which stands for Transport Layer Security,
and that's what's being used right now
to secure the data between your computer
and a website like Facebook or Dion Training or Amazon
or any of the other ones out there.
If you get that little padlock next to your domain name,
that means you're using a TLS connection.
This creates an encrypted tunnel
so nobody else can see what's inside it,
and that way they can't see your username, your password,
and your credit card information
as you pass it back and forth.
Now what are some examples of things at layer six?
Well, things like scripting languages
are going to be a layer six thing
because they're formatting data.
So if we're dealing with HTML or XML or PHP
or JavaScript, all of those tell the text-based ASCII
how it should display differently on the screen.
For example, I want to make this line bold
and make this other one underlined
and make this size X font.
Those type of things can all be controlled
using a formatting language like HTML
to take the ASCII code that you typed in
and translate into something
that looks better on the screen.
We also have things like standard text,
and this would be things like ASCII or Unicode or EBCDIC.
All of these are different ways of displaying text
from those ones and zeros.
We also have things like pictures.
We have GIFs and JPEGs and TIFs and SVGs and PNGs,
and all of these type of files.
They're all different ways of representing ones and zeros
as different graphical formats.
We also have movie files like MP4s and MPEGs and MOV files,
and all of these are going to show up
as some kind of video for us,
but they're all made up of these ones and zeros
in a particular format,
and that data formatting makes it into a movie
that you can watch just like this video right now.
So all of those examples I showed you so far
are all about presentation,
presenting text or images or photographs or movies
in a different way.
But we also have that example of encryption algorithms,
things like TLS and SSL.
Now these are taking your ones and zeros
and presenting them differently, right?
Because they're scrambling them up
so nobody else can see them,
and it secures that data in a jumbled format.
That's the idea here.
When you start dealing with TLS and SSL.
So it is a type of data format,
but it's not just a clear presentation
like we had with a movie file or a graphic file
or an audio file or text.
Instead, when we start dealing with encryption,
we're really focused on the security of the data
by scrambling it up and keeping prying eyes off it.