We want standardization.
The reason why I can take a copper ethernet cable such as this which has a RJ 45 connector.
Now we won't get into the details it's actually got a different name but most of us refer to this as
an RJ 45 connector.
I want to be able to take this and plug it into an HP laptop plug it into a Toshiba laptop plug it
into an ASUS laptop.
We won't worry about pronunciation for now but the moral of the story is I can take this cable and plug
it into different laptops because of this interface has been standardized and different vendors have
agreed to create the equipment to the specification or to the standard that makes life a lot easier.
In the old old days vendors just did what they wanted to.
They developed their own protocols and their own specifications which wasn't good for customers.
It was great for the vendor because if we bought their equipment you were locked into that vendor.
We don't want that as a customer as a customer.
We want to be able to buy equipment from different vendors and they should all be able to work together.
So because of standardization and because of the industry agreeing on specific models this cable can
plug into different vendor devices without any problems.
We take that for granted today but it was not always the case.
Now the first thing I want you to realize is and you probably know this already.
Nothing in life is as simple as it seems.
And people often have different viewpoints and debate often very heatedly about what is right and what
is wrong.
Don't get stuck in those debates. For the CCNA exam
just know that there are different models different viewpoints.
But there's one model that you need to know for the exam for the real world.
Have your opinion and go with your opinion.
There were different competing groups that were clashing about what was important and which protocols
should win the so-called protocol wars.
So we had the OSI Group with their protocols we had the TCPIP group with their protocols TCPIP is
one basically.
So for a long time we used the so-called OSI model to discuss TCPIP protocols.
But the TCPIP protocol is what we use in the real world.
We use IP version 4.
We use TCP, we use UDP, we use IP version 6, TCP, UDP, once again we use IP protocols in the real world.
So there's this disconnect if you like between the OSI model and the protocols that are actually
used in the real world.
So now in the new version of the CCNA we have what these called if you like a hybrid model or a combined
model of OSI and TCPIP model so don't get confused.
There was originally a four layer TCPIP model.
We have a seven layer OSI model but now we've ended up in summary with a five layer TCPIP model.
Five layers but we refer to the top layer as a layer 7 because it originated from the OSI model.
So I'm going to talk about some of the details now but in summary make sure that when you study for
the exam you understand that there's a TCPIP model.
But today we talk about five layers instead of the original four layers that were discussed in the original
RFC or request for comments requests for comments are a way that people discuss new protocols and
agree on what a protocol should be.
A protocol is basically a way to communicate.
So if I'm communicating with you in English we've agreed a certain way to communicate.
If I suddenly switch to another language and say, hu hanet fanda you won't necessarily understand
what I'm saying because that language uses a different communication stack if you like or a different
way to communicate versus English.
We have to agree on the protocol or language that we're going to discuss.
So RFC allow us to agree on what protocol will be implemented by different vendors so that it's
kind of standardized in the old old days we didn't have standardized protocols.
Every vendor did what they wanted but that was a total mess because she had different networks that
couldn't communicate with each other.
These days we want to have one network such as the internet that allows us all to communicate with one
another and that works because we've agreed on standards in the industry so different vendors Cisco,
HP, Juniper etc. will create equipment that can talk to each other based on the standard.
So, in summary, you need to know TCPIP model which today consists of five models for this currency CCNA
reflects the real world more than say previous models.
We have the OSI model which consists of seven layers don't get hung up on the individual layers and
I'm going to show you this practically using Packet Tracer.
Understand how the layers work you may get questions saying, Okay so at which layer of the OSI model
do you find HTTP which is a protocol used for surfing the Internet.
If you go to websites such as facebook.com you'll be using HTTP.
Actually today it's HTTPS which is encrypted HTTP it's more secure.
That is an example of what we would call a layer 7 protocol but you also need to understand in networking
that we'll discuss devices such as hubs and we'll say hubs are layer 1 devices hubs aren't really used
today but I'm going to discuss them just to give you an understanding because when you use a wireless
network things kind of change with Wi-Fi six or the latest release of Wi-Fi.
But previously everything acted as a pure hub in the air.
In other words only one person could communicate at a time.
Wi-Fi still like a hub because it's a shared medium that is shared so you need to understand the principles
of hubs.
Even though we don't use them physically today as in connecting cables to a hub but the air in wireless
networks is kinda like a hub.
We have switches which are called Layer 2 devices.
Actually some people would debate where the switches are a thing but we won't get into that.
We have bridges which are layer 2 devices.
We have routers which are layer 3 devices and we have what are called Layer 3 switches.
So notice I'm using terms here, layer 1 device, layer 2 device, Layer 3 device.
We have a layer 4 protocol which could be TCP or UDP and then we have Layer 7 applications such as HTTP
FTP, TFTP, telnet, SSH etc..
Don't get hung up on those, you need to know those protocols.
You need to know where they fit in the so-called TCPIP model or OSI model it'll come to you as we
do a whole bunch of labs and I'm gonna show you the protocols practically in Packet Tracer.
You'll see where those different protocols reside or set if you like in the model.