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. If you like this video, don't forget to like, comment and subscribe. The
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