1. Exploring the World of Network Models
LETS DO THIS!
Content based on: Managing and Troubleshooting Networks, Mike Meyers, Fourth Edition

2. GOALS FOR FIRST WEEK:
Describe how models such as the OSI seven-layer model and the TCP/IP model help technicians understand and troubleshoot networks
Explain the major functions of network hardware with the OSI seven- layer model
Describe the major functions of networks with the TCP/IP model

3. NETWORK MODELS – WHY AND WHAT?:
Why use a model to describe how a network works?
Networking is complicated!!
Communicate with others about what is happening and where it is happening
Two well accepted Network Models:
The Open Systems Interconnect (OSI) model
The Transmission Control Protocol/Internet Protocol (TCP/IP) model
Overall, these models provide:
A powerful tool for diagnosing problems
A common language to describe networks

4. LAYERS AND PROTOCOLS Each model is made up of several layers
There are specific protocols (rules, regulations, standards) for each layer
THE OSI model is the most widely used because its very specific about the layers and their functions
Let’s break down the layers through an example…

5. THE OSI SEVEN-LAYER MODEL IN ACTION
SO WHAT DOES THIS MEAN?
THE OSI SEVEN-LAYER MODEL IN ACTION
WWU Daily Operations Example:
One of the workers has just completed a new employee handbook in MS Word
She needs to transfer the Word document to the other worker for review
So what are her options to transfer the Word document?:
Flash Drive
Transfer file using the network
Let’s break down how she could transfer the file by explaining the layers
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical

6. HARDWARE AND LAYERS 1 & 2 LET’S EXPLORE Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LET’S EXPLORE

7. Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 1: PHYSICAL
The network needs a physical channel through which it can move bits of data between systems
UTP Cables:
Central Box:
The cables lead to a central box
Central box sends the data received from one system to all the other systems attached to it
LAYER 1: defines the method of moving data between computers
Anything that movies data from one system to another is in the OSI Physical Layer
Cables, fiber optics, radio waves

8. Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 1: EXAMPLE
The employee document can be sent from Janelle to Dana through cables and central hubs

9. Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 2: DATA LINK
Network Interface Card (NIC): The interface between the cables and the PCs
Cables run from the NIC in the PC to a jack on the wall or a hub
Inside the wall another cable runs all the way back to the central box

10. LAYER 2: DATA LINK HOW DO NICs WORK?
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 2: DATA LINK
HOW DO NICs WORK?
Each system (computer, device, etc.) needs a unique identifier
Kind of like an address or telephone number to know where the computer lives
This is the Primary Job of the NIC
The NIC has a chip that contains a media access control address, or MAC Address
MAC Address is ALWAYS unique
Example:
D-49
represents the NIC Manufacturer
Last six represent the serial number
The MAC address is printed on the surface of the chip and burned into the ROM chip:
D49
In computer terms:
D-49

11. LETS LOOK UP OUR OWN MAC ADDRESS
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LETS LOOK UP OUR OWN MAC ADDRESS
Click Start
Type cmd
Select the cmd application
Type ipconfig /all
Push enter
Your MAC Address is the physical address
Mine is DD-30-E1

12. INSIDE THE NIC: HOW ARE MAC Addresses Used?
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 2: DATA LINK
INSIDE THE NIC: HOW ARE MAC Addresses Used?
Computer data is binary
NICs send and receive binary data as pules of electricity, light, or radio waves
Example:
electric charge (pulse) is a 1 and no pulse is a 0
Flash of light is 1 and no flash is a 0
So…pulses represent binary data 1s and 0s
But how does the network get the right data to the right system?
Frames!
Pulse
Pulse
3 Pulse
2 Pulse

13. LAYER 2: DATA LINK INSIDE THE NIC: FRAMES!
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 2: DATA LINK
INSIDE THE NIC: FRAMES!
Networks transmit data by breaking down whatever is moving across the physical layer (files, web pages, print jobs, etc.) into chunks called frames
Frame: a container for a chunk of moving across a network
The NIC creates, sends, and receives this frame
Frame
I’m building a frame
Sends to central box

14. INSIDE THE NIC: FRAMES CONT’D!
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 2: DATA LINK
INSIDE THE NIC: FRAMES CONT’D!
A frame is made up of four general parts (see below)
Recipients MAC Address
Sender’s MAC Address
Type: specific network technology of the frame
(see
Data: the actual data file, etc.
frame check sequence (FCS): checks to see if the frame is structured properly and can be received and sent

15. HOW DO FRAMES GET TO THE RIGHT SYSTEM?
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 2: DATA LINK
HOW DO FRAMES GET TO THE RIGHT SYSTEM?
When NIC sends frame, it goes into the central box, or hub, or now in present-day called a switch. The switch determines the next steps for the frame
The switch stores information about the MAC addresses in its central database. Using this data, the switch determines whether the recipient MAC Address exists on the network
If the MAC Address exists, the switch forwards the data to the appropriate computer with the correct MAC address
If the MAC Address does not exist, the switch kills the transmission
Note: If the switch does not have the MAC Address on file, it will send a mass broadcast to all computers on the network asking them for their MAC addresses

16. THE COMPLETE FRAME MOVEMENT
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 2: DATA LINK
THE COMPLETE FRAME MOVEMENT
The operating system sends data to the NIC
NIC builds a frame to transport the data
NIC puts down the MAC access (recipient and its own) in the frame.
Waits for the cable path to be clear
Sends the frame through the cable to the network
Frame goes down the cable as pulses to the hub or switch which creates a copy of the frame and sends the frame to the correct MAC address
If a MAC Address is found, the frame is sent. If not, the frame is erased.
The NIC receives the frame
The FCS verifies that the data is valid. If so, the NIC sends the data to the software (the OS) to be processed.

17. Let’s Start on ICA#1

18. WHERE ARE WE IN OUR JOURNEY
DO YOU UNDERSTAND
LAYERS 1-2?
LET’S REVIEW!

19. TO INFINITI…AND BEYOND LAYERS 1 & 2!
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LET’S EXPLORE

20. PROBLEMS WITH JUST LAYER 1 & 2
Layers 1 and 2 are good for simple networks
Single switches
Remember…switches and computers broadcast to get MAC Address
For a small network, this works fine…
But what about for a HUGE network? One like the Internet??
PROBLEMS:
Millions of computers cannot broadcast over huge networks or else data will not get through – TOO MUCH GOING ON!!
Ethernet is not the only data/technology that flows through large networks; don’t know what to do with MAC Addresses
Solution: A logical addressing method not based on the physical machine
The entire Internet

21. LOGICAL ADDRESSING
Logical Addressing: ignores the hardware and enables breaking a large network into subnets
To move past the physical machine….need to create Network Protocols
Network Protocols:
Exist the computer’s Operating System
Create unique identifiers for each system that aren’t tied to the physical nature of the technology
Establish a set of communication rules for issues
Ex: how to chop up packets and get packets from one subnet to another
Two highly important network protocols that work together to deliver data:
IP (Internet Protocol)
TCP (Transmission Control Protocol)
Most networks today are based on TCP/IP network protocols
What do the protocols do??
LAN broken into two subnets
with five-computers in each
Single Switch;
10-computer LAN

22. ENTERING THE THIRD LAYER….
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical

23. LAYER 3: THE NETWORK LAYER INTERNET PROTOCOL (IP)
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 3: THE NETWORK LAYER
INTERNET PROTOCOL (IP)
What does IP do?
makes sure that a piece of data gets to where it needs to go
Gives each device on a network a unique IP Address (logical address)
Uses a unique dotted decimal notation based on four 8- bit number ranging from 0-255
Example:
No two systems on the same network share the same IP address!
By having a IP Addresses (not physical), networks can connect across data lines that don’t use Ethernet (such as phone lines)
What makes IP Addressing possible is the router, or magic box
Routers connect each of the subnets (magic box)
Routers use IP Addresses to forward data (not MAC Addresses)
Router:
Connects subnets to broader networks

24. LAYER 3: THE NETWORK LAYER INTERNET PROTOCOL (IP) CONT’d
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 3: THE NETWORK LAYER
INTERNET PROTOCOL (IP) CONT’d
So…Remember….in a Network powered by TCP/IP…there are two unique identifiers:
MAC Address (burned on NIC; don’t configure; physical address)
IP Address (software; configure; logical address)
Each computer has a MAC Address and an IP Address

25. LAYER 3: THE NETWORK LAYER
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 3: THE NETWORK LAYER
PACKETS
Network Layer contains packets that are created and addressed so they can travel from one network to another
For a TCP/IP Network to send data, there must be a frame and a packet
Frame: enables data to move from one device to another.
INSIDE THE FRAME IS A PACKET
Packet: Inside the frame there is an IP-specific container that enables routers to determine where to send data, regardless of the physical connection type, and the data itself
Each IP packet is handed to the NIC through the operating system.
The NIC encloses the IP packet in a regular frame
So how does this work…
One way to think about a packet
Another way to think about a packet
Data within packet
Packet
Frame

26. LAYER 3: THE NETWORK LAYER HOW DOES THIS WORK SO FAR
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 3: THE NETWORK LAYER
HOW DOES THIS WORK SO FAR
When you send data on the Internet to another computer, which is a TCP/IP network, data goes through many routers before it reaches its destination. Here’s what happens:
Along it’s journey, each router receives frame and:
strips off the frame
determines where to send the data based on the IP Address in the packet
Creates a new frame
Sends new frame with packet enclosed along its way
New frame will be correct frame from appropriate technology (DSL, phone line, for example)
When frame and packet finally reach the correct destination subnet’s router, the router:
the destination IP Address
Create a frame with appropriate destination MAC Address that matches the IP Address and send it to appropriate computer
The NIC then receives the frame and passes off the packet to packet-specific software that knows what to do with the packet, which handles the rest of the process (layers 4-7)
IMPORTANT!! The NIC can’t handle the packet, only the frame, but needs the MAC Address so it can receive the frame
So…The NIC is still highly important because it is the connection between the hardware and software

27. WHERE ARE WE IN OUR JOURNEY
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
WE HAVE COVERED LAYERS 1-3
Layer 3 is the LAST layer
To deal directly with hardware….

28. NOW…LET’S GO INTO LAYERS 4-7 Layers 4-7 work strictly with:
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
Remember…
Layers 4-7 work strictly with:
SOFTWARE
LET’S EXPLORE!

29. LAYER 4: THE NETWORK LAYER ASSEMBLY AND DISASSEMBLY
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 4: THE NETWORK LAYER
ASSEMBLY AND DISASSEMBLY
Data must be CHOPPED UP before they can be sent across a network
To send data across a huge network, a computer must be able to:
chop the data into chunks that will fit into a packet (and the NIC’s frame)
organize the packets
Hand them to the NIC
To receive data, a computer must be able to:
Recognize a series of incoming packets
Reassemble the packets correctly
Verify that all the packets arrived in solid shape
The Transport Protocol breaks up the data into chunks called segments or datagrams
The Transport Protocol gives each segment of data some type of sequence number (datagrams don’t get sequence numbers)
Embedded into the data within each packet is:
a sequencing number
The total number of segments so the system can put the data back together
In other words…
The TRANSPORT LAYER establishes an order for the data within a packet so that it can be disassembled and reassembled

30. LAYER 4: THE NETWORK LAYER REQUESTS UNRECEIVED DATA
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 4: THE NETWORK LAYER
REQUESTS UNRECEIVED DATA
Overall, we talked about how the TRANSPORT LAYER:
Assembles and disassembles data, puts information into the packet
The TRANSPORT LAYER also
Initializes requests to receive packets that weren't received or were corrupted
Basically, the transport layer uses it’s software to ask the sending computer to resend a packet or two that may have been lost or corrupted

31. WHERE ARE WE IN OUR JOURNEY
DO YOU UNDERSTAND
LAYERS 1-4?
LET’S REVIEW!

32. ON TO LAYER 5! 5 Alive! Layer 7 - Application Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
5 Alive!

33. LAYER 5: THE SESSION LAYER
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 5: THE SESSION LAYER
WHAT IS GOING ON?
Remember…software assembles and disassembles packets (layer 4), what happens next?
On a network, computers and other systems talk to each other ALL THE TIME (see example)
Such talking occurs through the TCP protocol: enables two hosts to establish a connection and exchange streams of data
In other words, there are requests being sent and received to computers, severs, etc. ALL THE TIME
Print jobs, web addresses, accessing files, etc.
There must be a way to handle the multiple requests:
Must be a way to direct incoming files, print jobs, web pages to the right computer or printer or server, etc.
Operating system must enable one system to be able to connect to another system to verity that the systems can handle the request
Example:
If my computer wants to send a print job to the printer in PH029, my computer contacts the router/switch associated with the printer to see if it can handle the print job
This is accomplished through the SESSION SOFTWARE and is the core of the SESSION LAYER
The SESSION LAYER handles all the sessions for a system. Specifically it:
initiates sessions
accepts sessions
opens and closes sessions

34. Select the cmd application Look at all the sessions!
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LETS SEE OUR SESSIONS
Click Start
Type cmd
Select the cmd application
Type netstat -a
Push enter
Look at all the sessions!

35. WHERE ARE WE IN OUR JOURNEY
DO YOU UNDERSTAND
LAYERS 1-5?
LET’S REVIEW!

36. ON TO LAYER 6! 6! Layer 7 - Application Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical 6!

37. LAYER 6: THE PRESENTATION LAYER
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 6: THE PRESENTATION LAYER
WHAT IS GOING ON?
The PRESENTATION LAYER translates and coverts data from lower layers into a format useable by the application layer and vice versa
In the OSI Model, the protocols that function at this layer are not so clear cut
For example, TLS (Transport Layer Security) and SSL (Secure Sockets Layer) protocols encrypt and decrypt in layer 6, but initiate in layer 5
That is all I expect you to know for now

38. LAYER 7: THE APPLICATION LAYER
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
LAYER 7: THE APPLICATION LAYER
WHAT IS GOING ON?
The APPLICATION LAYER involves the actual applications you and I use everyday
Windows 7; Google Chrome
You use and experience a network through an application
IMPORTANT: the APPLICATION LAYER does not refer to the applications themselves, but to the code built into all operating systems that enables network-aware applications
In other words, Layer 7 involves more the application programming interfaces (APIs), which enable programmers to make software applications network-aware

39. That was an epic adventure through the 7 layers of the OSI Model!!
OUR JOURNEY CONCLUDES
That was an epic adventure through
the 7 layers of the OSI Model!!

40. Let’s Work on ICA#1: Part 2