since we've looked at the OSI model, one other model that we need to mention is the TCP IP model
not going to spend a ton of time here because I really do believe the focus will be on OS I. But the Department of Defense came up with a four layer model that maps roughly to the S I model.
What I would do is focus all my effort on OS I and remembering the chart we looked at in the last section. Make sure you know your layers from top down seven all the way down to one
from application down to physical and what happens at each layer
now on the T. C P I P model, what I would focus on is being able to map each layer to the OSC.
in the OSI Reference model, our top three layers are application presentation session.
They're all wrapped into a single layer called the application layer on the TCP I P model. So that's not so bad.
Now the transport layer is called the transport layer, easy peasy. So far,
the network layer of OSC is referred to as the Internet or the Internet, working layer, and then the bottom two layers of OSC data link and physical are combined into the network interface layer,
so it's not going to be very difficult to memorize this mapping.
But what we do put that additional focus on is the D. O D model, because it really focuses on the TCP I P elements.
Like we've said, this is going to be the basis for a lot of our discussions. Throughout this course
the TCP IP Protocol,
you will hear questions about it on the exam.
Make sure your brain isn't too focused on C
for me, somebody who has been teaching the OSC model for 20 years. When I see the question on what Layer does a router operate? I immediately say layer three the network layer.
But if I'm not careful, I can miss at what layer of the TCP I P. Layer does a router operate?
And that's going to be the Internet layer.
So you want to be very mindful of those questions and their wording.
Focus on OS I and know the mapping of the TCP I P layers of their model
as we focus on TCP IP, one of the most important things where we should direct our focus in the open nature of the protocol.
Again, if you go back to the late nineties and early two thousands, there are lots of different operating systems that required specific protocols.
Novell used I PS PX You next use TCP I P.
But Windows was using that be IOS and Apple systems were using Apple talk. So many protocols,
like I mentioned earlier in the course. If you have too many protocols getting converted, you can have gateways that provide translations. But things get lost in translation.
So what we really wanted to do was standardize.
Let's get all the operating systems on board the same train.
The reason TCP IP was chosen is because it's an open protocol.
When we talk about the openness of TCP IP, TCP I P is created by the community.
It is modified by the community.
At any point in time. Anyone can view the details of TCP IP, which is really very helpful from an operating system standard.
It's not something that's owned by Novell or Microsoft, but it's open and owned by the community.
When we talk about being able to modify TCP, I p or even the fact that it's created by the community the documents that detail of requirements and the function of T C P I P.
These are called our FCS crests for comments.
Each element of the design and the function of TCP IP is documented in RFC or multiple our FCS
so often their proposed changes
once an RFC is approved and implemented, if there's a modification or an enhancement that RFC actually doesn't get updated,
there's a brand new RFC that's assigned to it.
The only time you add up updates is before an RFC is approved.
That's kind of interesting. So it's just one of those things about how requests for comments are managed.
I put it on the slides because I think it's possible that it could be a turkey question that they don't update our FCS, but they create brand new RFC numbers and go from there.
There is some information on rfc editor dot org. So if you're looking for something fun to do on a Friday evening, you might want to visit that webpage and check it out a little bit.
Or if you type out specific RFC s, you can look at an RFC and see the details
later. When we talk about I p address ng, we'll talk about how certain I P addresses are reserved for private use.
So after you're done reading RFC editor, you can look up a specific RFC. And again, if that doesn't fill up your lonely Friday night, then nothing will.
All right. Just a quick review of the TCP I P model
TCP I. P is such an important suite of protocols because of the fact that it's what just about every operating system is using today.
It's an open protocol.
You can view the contents of C C P I. P through various documents called requests for comment.
Remember the OSI model and the TCP I P model closely mapped to each other.
So if you want to understand any of them, you can view the two together on the previous screen I showed you.
I would certainly memorize the OS I model and give that my top priority. But I would know the TCP I P model and how it maps for that occasional question that might show up on the exam