The OSI Model: Part 1 - Physical Layer

Video Activity
Join over 3 million cybersecurity professionals advancing their career
Sign up with
Required fields are marked with an *
or

Already have an account? Sign In »

Time
15 hours 43 minutes
Difficulty
Advanced
CEU/CPE
16
Video Transcription
00:00
>> The OSI model was designed to provide
00:00
practical guidance on creating standards-based elements.
00:00
Whether they are hardware, software protocols,
00:00
firmware, at any rate,
00:00
the focus is on creating standardization.
00:00
It was not designed to be taught in classes or to
00:00
be enforced to be taken to 100 percent as it is.
00:00
It was designed to be a very flexible model
00:00
to just give guidance.
00:00
But it does help,
00:00
when we look at the OSI model,
00:00
we look at each layer because we can learn
00:00
a standards-based device at
00:00
this layer does the sorts of things.
00:00
It's easier to understand networking
00:00
when you look at it in relation to the OSI model.
00:00
Even though the OSI model is a top-down model,
00:00
which means ascending computer
00:00
first uses the application layer
00:00
then the presentation layer,
00:00
then the session layer and so
00:00
on to send data from point A to point B,
00:00
it's actually easier to understand from the bottom up.
00:00
We're going to start out with the physical layer.
00:00
The physical layer is known as Layer 1.
00:00
It's best to start out here
00:00
in learning networking because
00:00
your least-complex devices are
00:00
down at the physical layer.
00:00
By the way, I love this image,
00:00
and I probably wouldn't love it so much if I hadn't
00:00
seen server rooms that look like this.
00:00
This one makes me think of,
00:00
I think the cables have just gotten tired of this guy,
00:00
and the racks and the cables have
00:00
just decided to swallow him whole.
00:00
That's what it makes me think of.
00:00
Obviously, this's not very neat and clean setup,
00:00
and very difficult to
00:00
control and to troubleshoot and fix.
00:00
But with the physical layer,
00:00
what we're talking about is these devices
00:00
that don't have any understanding of the data.
00:00
They're simply there to provide
00:00
a pathway and a means for data to travel.
00:00
For instance, let's think about cable.
00:00
Cable doesn't know what type of data is traversing.
00:00
Cable doesn't care what protocols
00:00
being used or where the destination is.
00:00
It's just simply providing a pathway for data to travel.
00:00
Hubs. Hubs don't care where data's going.
00:00
Hubs send all data out all ports all the time.
00:00
It doesn't do any addressing or error detection,
00:00
in which part of the reason we don't use these anymore.
00:00
I hope you're enjoying my little diagram of
00:00
the dinosaur running off with the hub in its mouth.
00:00
That's to indicate we don't use hub so much anymore.
00:00
But the idea is,
00:00
hubs weren't even powered when I got into IT.
00:00
They were just metal racks that
00:00
you plugged the connectors into,
00:00
and it provided a conduit for the signal to travel.
00:00
There's no knowledge or understanding with cable,
00:00
there's no knowledge or understanding with hubs.
00:00
Also, your network card
00:00
has a physical layer element as well,
00:00
because there's a portion of
00:00
your network card that's just to plug the cable in.
00:00
As a matter of fact,
00:00
all your network devices that are
00:00
hardware have to have the physical layer element.
00:00
You've got to have somewhere to plug the cable.
00:00
That's physical layer stuff,
00:00
just basic connectivity, getting the signal on the wire.
00:00
The network card itself does more complex functions,
00:00
but there is a portion
00:00
of the network card that's Layer 1.
00:00
In this section, we mentioned
00:00
that these are just our basic physical devices.
00:00
When we look at threats related to Layer 1,
00:00
we think about things like theft.
00:00
We think about vandalism.
00:00
We think about tapping into a network,
00:00
eavesdropping on the signal, traversing the cable.
00:00
Also in the middle I have
00:00
little illustration of a Faraday cage,
00:00
and that's designed to prevent signal leakage,
00:00
because if we have signal leakage,
00:00
an attacker could analyze
00:00
that leakage to determine
00:00
information about what we're transmitting.
00:00
Analyzing that signal, that's Layer 1 as well.
00:00
In this section we talked about the physical layer,
00:00
Layer 1 of the OSI model,
00:00
and just covered the very most basic elements.
00:00
They have no intelligence,
00:00
no knowledge or understanding of the data.
00:00
They simply provide a pathway
00:00
and a means of getting signal
00:00
on the cable and convert it to electronic signal.
Up Next