Network Models

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Network Models

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1 hour 20 minutes
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Network Models

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Hi. Welcome back to the network plus Certification video series on Mike Redman, master trainer here to help guide you through your successful journey of becoming a network plus certified technician,
we're gonna walk through a wide variety of topics, starting with basic network concepts all the way through network management and security. In this segment, we're gonna talk about network models.
I'll describe how models such as the seven Layer model and the TCP I P four layer model helped technicians understand and troubleshoot networks.
I'll explain the major functions of network hardware and the seven layer model as well as described the major functions of networks with the TCP I P model.
I'll help you compare and contrast the difference between TCP and UDP and define and exemplify some frame packets, segments, data, grams and ports.
So as we begin our discussion, you need to understand that this chapter is the cornerstone for everything else that we're going to talk about. Over the course of this certification. Siri's.
It all starts with the two different models. We're gonna start with the OS IE seven layer model. This provides and powerful tool for diagnosis. It's a common language. If you will between network administrators to describe networks and how they're connecting and communicating.
then we have the TCP I P model. It's just another model that we will describe indepth a bit later on it. Understand that it describes the actual de facto protocol of the Internet. It's how the Internet works. Each mayor
of the TCP I P model you may often see it referred to is the deal D Model
maps directly to the OS I model Very well.
So first, let's start with model concept.
In general, a model has a look and feel of the actual thing. So we use these models to help conceptualize and troubleshoot our networks with that understanding will then go into the O Side seven later model and the TCP I P model
to see how they helped clarify network architectures. For technicians,
the best way to learn the O. S. I and T C P I. P models is to see them in action.
So let's talk about models.
What is a model?
We have lots of them around us. Computer models that predict the weather, plastic model, airplanes, fashion models, they're all models.
The model has the later functions of the rial item.
So there are different model types, especially when we start talking about networking these two models. Theo Asylum model in the TCP I P Layer model, these models actors guidelines and break down how a network functions into discrete parts called layers.
All models are simplified representations of the real thing.
The main benefit is that now we have a tool that we can use to provide powerful mental diagnosis to problems that help zero in on a solution.
They provide us a common language to describe our networks. It's a way for us to communicate with each other about the functions of the network.
So with the seven later model who was originally proposed by the International Organization for Standards Works for almost every type of network, each layer is well defined with a function and a related protocol.
So here is the OS ie seven layer model, physical layer, Datalink network transport session presentation and application.
So let's look at each of these layers a little more in depth, starting with layer one. This is your physical layer. This is when your cabling in your actual radio waves or carrier signal waves resigned. Ah, hardware devices like hubs
and your network interface. They all live
in the physical layer. That's the first thing that you can touch. They connect to layer to the data link layer. That's where your switch is live.
So just to try to think it through, let's say that we have a worker that has just completed a new employee handbook. She wants to transfer that war document to another worker for her to review before sending it to the boss, Gen. Ellen Donna,
here hard at work with a simple problem.
Networking is how we fix that.
So there are multiple things that she could do. She could copy them to a flash drive, for instance, and walk it over. We call that sneaker netting. It is a form of networking,
or she can transfer the file using some sort of Elektronik medium.
That would be the network,
at its heart, at the very base of everything it starts. Like I said at the physical layer, this is the personality of the network of you will. It's your cabling. There are several different kinds of cables that you're going to need to be familiar with to successfully navigate the network plus exam.
We're going to start with the UDP cable, probably absolutely the most
common type of cabling in modern networks. You TP is unshielded twisted pair
next physical equipment like a hub. Each computer system has a cable leading to a device that that device often will be called a hub.
The hub sends the data received from any individual system,
and then all other systems connected to that hub received that data. It's a large broadcast domain.
So now, as Donna prepares to hit send, we've taken care of the physical layer. We understand the medium and media that it will travel
next. We need to begin moving up the OS I model. This would be layer to this is where switching happens, your switches and bridges and your network interface cards. That is a layer to device it provides for physical addressing of machines.
Here's a look at a typical Mick.
This is the device that your network cables are plugged into
the cable runs fromthe nick and the PC to usually a jack on the wall. The cables run through the walls to a closet in that closet connects to usually switch or a hub.
So I understand that your Nick, like I said, is your physical address. Each system on a network must have a unique identify wre. We call that the Mac address or the media access control.
It's a unique address burned into the wrong trip of the network card itself.
Each Mac address is 12 Hexi decimal characters, or 48 bits in length.
So if you want to, for instance, view your Mac address on a Windows PC, it's a simple is opening up the command line and typing I p config space backslash. All that will give you along with many other pieces of configuration information. You can view your Mac address of your machine
so thes Mac addresses, as I indicated or unique to every machine. The Institute of Electrical and Electronics Engineers, or IEEE, controls and issues Mac addresses to hardware manufacturers.
This standard is also called Mack 48 or You I 48 extended unique, identify rhe. Each Hexi decimal character represents four bits. It takes 12 Hex Character's too
represent the entire 48 it's broken up into 2/2 the 1st 6 digits or unique and specific to a manufacturer. The last six dates are going to be the serial number for that device. There are no two same Mac devices in the world.
So now we have our physical layer and we're starting to understand layer to We're about ready to put the data on the wire. First, we need to understand how our data moves. It's it's in a digital format. If I were to put Elektronik stream of data
threw in a Silla scope, it would be choppy and
blocked up. Kind of like this,
however, this needs to be translated by your computer and understand. Your computer only understands zeros and ones. So the same Acela scope data now to your computer looks like this. Each up wave tells the computer that the bit is turned on
a down wave. The bid is turned off,
so 1010111011 matches the waves of the Acela scope.
So say hi to our friend Nick.
Nick now needs to sin data across the network, so Nick has a job to do, and as we continue, we're going to help nick out.
It all starts with a frame. Frames are made up of fields that contain information. For instance, frames contained the recipients. Mac address the sender's Mac address the data itself and a small piece of the end called the F. C s. That frame check sequence.
This is forever checking to make sure that the data gets there in one piece.
You can think of this frame as a canister, much like you'll use that your bank drive through it contains all of this information that we now need to put on the wire.
Different networks used different size frames. Many frames hold about 1500 bytes of data. The sending software breaks up large amounts of data into those smaller chunks. The receiving station then put the chunks back together in proper order.
So when connected to the hub, all devices on the network see the frame. But on Lee, the device that it is addressed to will process it. So every frame is received by every Nick. Remember, I explained it was a large broadcast on me.
We'll get into the broadcast remains a little later,
however, understand At this point, all we're trying to do is get our data from one machine to the next that is what the Mac address helps us do.
So since the cable is shared on Lee, one system can speak at a time. It's only polite to take turns processes used to keep tunics from talking at the same time.
So now we're beginning to understand. This is how computers
take turns on the line to make sure that they don't interfere with another individual's communications. So usually two devices have talked before, so the destination Mac addresses are already known. However, if the Mac address is not known, a broadcast message is sent out over the network. It's
also represented in all Hexi decimal characters looking like a Mac address. Because,
remember, every machine needs to be speaking a common language, and at this layer, this is the only language that they know. So the broadcast address is formed by Hexi Decimal characters.
So now Neck can begin the process of doing his job. He has his frame. He has his data. He's begun to put it all together. Now he needs to receive that command to send the data, and that is when Nick actually begins building the frame. When you hit. Send
now, when the frame is received by the receiving computer that receiving station checks the F. C s.
If the value matches, then the Nixons, the data portion to the network operating system for further processing. If the values don't match the frame has errors and must be recent.
So I indicated that we were dealing with a seven layer model. It's
mostly true, however, Layer to is broken out into two sub layers. The media access control layer, the Mac and the logical link control
that is the helper. If you were to get to the next layer, where the logic of the network lives,
this is the only layer that's broken out into those two sub layers. So don't worry about the rest. This is the only one that you'll need to remember
next. Let's continue watching our data flow across the network.
We're now at Layer three. This is the network layer. This is where routers in multilayer switches live.
This is the layer that handles logical. Addressing containers called packets are what reside in this layer. We're no longer necessarily within frames. This is where you find T. C. P and U T P. These are the protocols that the network layer understands
there are others, but these two are the most dominant.
This is where we find the TCP I p sweet made up of TCP the transmission control protocol and I p the Internet Protocol. Like I said, there are some others, but those really buying larger just not used anymore.
So I p technology Now we need to understand a different way of counting. Numbers were no longer counting numbers in Hexi Decimal for Nat. Now they've changed you dotted decimal notation. They range from 0 to 2 55 You've probably seen an I P address. It looks like this 192168
101 23.
This is a logical address for the machine. It is away from the physical addressing that we have done at layer to
this is the way we break out our larger networks into sub nets.
So let's talk about these devices. These devices called routers, routers used to chop up large networks into smaller networks, rodders forward packets by their logical address. That's where we find again the i p addressing an I P router, which is the most common
forwards. Those I p packets
this is only being performed. Layer three, the network layer.
So a common I pack, it looks like this destination i p. The source i p and the actual data that it's carrying. So far, Nick seems to be doing a pretty good job.
So now we have frames and packets within those frames. Network software creates a packet that contains the sending and receiving I P addresses. Along with all that data. You need a couple more pieces of information like the data type in the PAC account, but we'll get into that again later.
So now we have our packet that is enclosed within the frame that contains the sending and receiving Mac addresses as well as the I P information.
This is how we connect to the network or the Internet. The router connects a local network to the Internet. The local hover switches, in turn, connected to the router, and the router is connected to the Internet through a cable or a phone line.
The cable or phone line used a different kind of frame, so the router strips the frame and creates a new one.
So now we have our router doing what routers do best the router replaces the Mac address with the type of address used by the cable or phone company. The frame uses the I P address to guide it to the receiving station. Once it arrives,
the receiving rounder strips off the cable or phone companies special frame
and adds the Mac address of the receiving station. Then that Nick will strip off the Mac header and hands the frame off to the network operating system.
Next, let's talk about layer for the transport layer. This is where assembly and disassembly began to happen. Most data is much larger than a single frame. A network protocol is needed to chop up the data into smaller packets and give each one a sequence number. We've talked about that.
The sequence numbers are used by the receiving system
to put the packets back and order. Remember, the Internet is wide open space. Every packet knows where it needs to go, but your data doesn't necessarily travel in a sequential order. It just knows it needs to get to its destination. It will be reassembled once it arrives.
This is a little like how UPS delivers boxes. Lots of boxes coming from lots of different places, but only to one single address. That is how the transport layer works.
Primary protocols that we deal with in the transport layer or again TCP Judy P and S P X.
So TCP transmission control protocol is a connection oriented protocol. It's built on a foundation of what's called the three way handshake. Will discuss that a little layers. Well, they are sin and AC
packets designed to verify end in connective ity. It verifies that packet delivery in recent if a packet is dropped thes synchronizing acknowledgement packets. They travel through specific ports ranging from 1 to 65,535.
Then we have UDP or the user data Grand Particle. This is a connection less oriented protocol. It's a best effort. There's no connection or packet delivery verification.
So within Layer four, we have specific service. Is that happen? Segments, data grams assembly in disassembly, reliable or unreliable delivery of your data and information error correction and flow control.
The transport layer is also where the initialization of request for packets that weren't received in good order comes from
next. The session layer layer five understand that it is possible to have a conversation with more than one person. For instance, you could be on the phone talking to one person while sending an email to another and perhaps sending a text message to a friend
all simultaneously happening together.
This session layer is
what manages all those different types of communications. The software that handles these processes is called the Sessions Software. It only works at Layer five.
This is where synchronization begins to happen. Session establishment tracking in naming it initialize is sessions except incoming sessions opens and closes existing sessions. This is also where we begin the practice of security and name recognition and auditing.
Some of the Layer five protocols are Net BIOS and RPC Remote procedure. Calls happen at Layer five.
Next, we have Layer six. This is the presentation layer. Tasks are solved here at this layer. Macs and PCs, for instance, is not always talk the same language, however, In an effort to coexist, we had to figure out how to allow someone with a PC
to communicate with someone with a Mac
so it layer six. The presentation layer. We've standardized the formats
to allow every different type of operating system to be able to
seamlessly exchange data.
This is where you'll find protocols such as J Peg Tiffin gift files. This is also where t l S and S S L live were handling data encryption and decryption and layer six,
and finally layer seven The application layer protocol users used the Application Layer network application to exchange data on the network. This is where, for instance, Windows Vista in Window seven. Live Web browsers. Outlook.
All live in the application layer.
It is the layer that is interacted with by the users.
This is where we handle our resource sharing and directory service is like active directory. This is where our email is handled. A some TP simple mail transport protocol.
So now let's talk about the
four layer model. The D o D o T c P i p model.
Understanding that the OS I model was developed due to a need to standardize hundreds of different protocols made by different manufacturers. In the end, one protocol sweet, really one out. It's now the defective standard for the Internet. It's T c P i P
TCP I P is both a protocol and a model.
The TCP I P model layers map to the corresponding OS I model layers.
They performed the same functions and use the same technology protocols, Service's and devices. Some layers map directly to the corresponding layers, while other ones have more of a correlation.
So T. C P. I. P does not have a standards bodied like Theo S I model does. This is the result of many interpretations and variations within the models. Variations used in the exam is the most popular used by major manufacturers like Microsoft and
However, this variation uses four standard layers the Link network interface, the Internet layer, the transport layer and the application layer.
The application layer, much like layer one in the OS I model, corresponds to the layers one in two.
It handles the physical elements of the network cabling, hubs, physical addresses or your Mac address software and higher level protocols work in the higher level layers of the TCP eyepiece stack. This is also where you'll find your frames. However we end the TCP I P model.
They're referred to as PT use or
protocol data units.
Next, we have layer to this is the Internet layer. It deals with any device or application that uses I p protocols and I p addressing as well as routing routers function in this layer of this model. This maps directly to layer three of the O S I model.
Now the PT use at this layer are called
Layer three is the transport layer. This layer maps to the OS I transport layer as well as this session layer and some of the application layer uses two protocols TCP and Judy P
improvised boast connection oriented in connection, less communications just like the other model.
Now the PT use our segments with TCP and Data grams with you t p.
So we've discussed how TCP provides a connection oriented communication. It's important to understand what types of applications you're talking about. You're talking about http and pop web and email. These all require good, established, reliable communication.
TCP flows A prescribed set of procedures to establish
keep a good connection synchronizes the session between transmitting and receiving hosts.
UDP The connection less communication used by some of the upper layer protocols that don't require reliable verified connections. UDP since data without waiting to see if the receiving system is even ready to receive it protocols and applications like
streaming audio and visual Indian s queries
be HCP broadcasts.
So each TCP segment contains a header of information that's such a CZ, the source and destination port, the sequence, the acknowledgment, numbers and flags to ensure that connections are established and verified. Data follows Then that TCP header information
with UDP Data Grams.
They only have four header fields. No mechanisms are built in to establish, verify or track connections. And after those four fields, your data will follow that UDP header information.
And now we have the top layer of the TCP I P model. It's the application layer. This maps directly to the top three layers of the O S. I model. It contains the applications that you're probably most familiar with, like D N S. D. A, c p and http.
It allows a presentation layer formats such as mime or
email and application later, AP eyes.
So with each layer of both the O. S. I and the TCP I P model, we deal with the method called encapsulation. These models encapsulate data by adding headers in front of the data to be able to pass it on up and down each of these models stack.
The data is called or known by different names as it travels to reach later.
So these names are called protocol data units.
You should know and understand the concept of the caps elation because you will begin to hear it more and more as we discuss deeper and deeper networking concepts.
So one more important set of tips for you, you absolutely must memorize the O S. I and the TCP I p layers
A simple pneumonic for the O S. I layers are all people seem to need data processing that will help you keep them in order from 1 to 7. Remember, only the datalink layer is the layer that is broken up into two sub layers. The media access control and the logical link
And remember, at which layer encapsulation happens,
all of them must encapsulate going up and down the stacks.
Well, they haven't pretty simple, right? I know it could be a lot of information coming at you all at once. But don't worry. I'm here to guide you every step of the way you can do this. Just remember, study hard lots of practice questions
and you will succeed.
You will become a network plus certified technician. I'll see you next time
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Network Architecture

In the Network Architecture Course by Michael Redman, students will get a thorough deep dive into network architecture, focusing on core concepts that will help them pass the Network+ exam. You will learn about network models, cabling, and technology.

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