Hey whats up guys? Welcome to CertBros
In this video, we're going to be talking about the TCP/IP model
Quick warning, we're going to be referencing the OSI model a lot here
so if you haven't already watched that video check that out first then come back
ok so what is the TCP/IP model? It's a model to
standardize computer networking. Sound familiar? It should because it's the same
description as the OSI model. Now the OSI model while widely
referenced isn't used in the real world the TCP/IP model, however, is the real deal
Thankfully is not that different here is the TCP/IP model.
Four simple layers, application, transport, internet and link
And just like the OSI model, it's numbered from the bottom up, but the direction depends on if you're sending or receiving traffic
So this is the original model but it has been updated
Here is the brand new freshly designed model
One extra layer and one renamed layer
that's it
the link layer has been split into datalink and physical
and the internet layer has been renamed the network layer
simple right?
It gets even better when we compare the TCP/IP model to the OSI model
Now if you remember the OSI model has seven layers compared to our five here
but when you look at it you'll notice the application presentation and
the session layers are just shown as application layer in the tcp/ip model
all the other layers line up nicely which is great because we should already
know the concept of how this works
So let's remind ourselves about the
protocols and devices at each layer. At the application layer we have
application protocols such as HTTP FTP and SMTP.
The two most common transport protocols are TCP and UDP. Port numbers are also added here. At the network layer
we have the Internet Protocol or IP. Routers also operate at this layer.
The data link layer contains ethernet
Switches typically at this layer, although you can get layer 3 switches that have some routing capabilities
Finally, we have the physical layer. Think of everything we
can touch and feel here. Things like cables and network interface cards
Ok, so as we send data each layer will add its own bit of information. This process
is called encapsulation. When we hit the physical layer the data is transmitted
over to the receiving device. The receiving device then starts to
decapsulate the data. We saw this in the OSI model but in this video we're going
to take a closer look. We start with our application data at layer 5 this is then
passed down to the next layer where the transport information is added. Let's say
is a TCP header. Each time a header is added this will contain specific
information. For example a TCP header will contain things like the source and
destination port number, sequence numbers and a few more bits of information.
We'll go over this in more detail in a separate video. We then move to the
network layer where we add the IP header. This will contain the source and
destination IP address as well as some other bits of information. Lastly we have
the data link layer. Here we add not only a header but a trailer as well. The
header contains main lead the destination and source MAC address and
the trailer contains some error checking information that the receiving side can
check and make sure the data has been received correctly. Once the data hits
the physical layer it is physically transmitted
so we've gone through the encapsulation process. It's important to note that at
each stage the data has a specific name. At layer five the data is called, well
it's just called data at this stage. Once the transport information has been added
it's now called a segment. Adding the network layer information makes our
segment a packet and finally once we add our data link information the packet
becomes a frame. Now once data has been transmitted the receiving computer decapsulates
the information. It will check the destination MAC address for that
frame and if the frame is destined for our computer it's processed further
the computer then checks the IP information off the packets again if the
packet is destined for our computer is processed further.
The transport information is read and the application data is sent to the receiving
application. So that's it for the TCP/IP model after looking at the OSI model
thankfully there isn't much else to learn. This video is part of our full
CCNA course which can be found in the description.
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thank you for watching