1.1 Introduction to the OSI Model

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  1. Physical: Ensures the physical communication between the devices and converts an electrical pulse to binary. It defines the specific standard to which the physical components must comply to. The most commonly used protocols include the following, IEEE.802.11, IEEE.802.3 and several others.
  2. Data link: The Data link layer provides communication between directly connected devices. It also provides error handling for the OSI model's physical layer. It consists of two sub-layers, Media Access Control (MAC) and the Logical Link Control (LLC) layers. Most switches operate on the Data link layer or Layer 2 for communication, but there are exceptions where switches can also work on Layer 3 and are referred to as a Layer 3 switch where routing capabilities are required.
  3. Network: Routers function on the Network layer. This layer is responsible for forwarding packets to specific routes on the network. This layer analyses the packets received and determines if it has reached its destination and then passes it to the Transport layer. If it is not the final destination, it will pass it to the Data link layer until it reaches its final destination. The Network layer is also responsible for updating routing tables.
  4. Transport: The Transport layer’s function is to deliver data across network connections. The most commonly used protocols are TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). Different protocols will have different functionalities when transporting data across the network. For example, error checking is done using the TCP protocol.
  5. Session: The OSI model's Session layer manages the flow and sequence of different network connections. This ensures the possibility for dynamic concurrent connections.
  6. Presentation: The simplest part of the OSI model is the Presentation layer, as it handles the processing and converting of the data, for example, encryption and decryption, to facilitate the support for the Application layer.
  7. Application: The final layer in the OSI model, the Application layer, provides network services to the application. These services include protocols that integrate into the application; for example, the HTTP protocol is used to deliver data to a web browser to display a user's web page.

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https://sites.google.com/site/osimodellayers/layer-3---network
https://community.cisco.com/t5/image/serverpage/image-id/34062i95AA8ACC6BD9290D/

OSI TCP/IP - Comes from DoD (Department of Defense)
1 Physical Please Network Never
2 Data Link Do Network
3 Network Not Internet Ingest
4 Transport Throw Transport Toxic
5 Session Sausage Application Apples
6 Presentation Pizza Application
7 Application Away Application

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http://www.gocertify.com/quizzes/osi/

Physical Layer- Layer 1
What we can touch, measure and see
Uses logical addresses to route data

PDU/Protocol Data Unit - Bit / 1, 0
This layer converts packets from the data link layer into electrical signals
Cables
NIC - Network Interface Card

Ethernet settings
Network and Sharing Center
Change adapter settings
Network Connections
Right click Ethernet - Properties - Configure
Details
Property - Hardware IDs
Is Connected
If true - Physical connection looks good

Data Link - Layer 2
Provides point to point connectivity within our network
Ex - packets to a switch,

PDU/Protocol Data Unit - frame- Segment of data with beginning and end
The Data Link layer is composed of two sublayers: the Logical Link Control (LLC) lower sublayer and the Media Access Control (MAC) upper sublayer. Components/protocols relevant to the Data Link layer include driver details, MAC filtering, and ARP tables.
Responsible for framing, error detection and physical addressing
A MAC address is a 12 digit hexadecimal number, which is a physical address of the network components.
Switches operate at this level and maps to MAC address
EUI-64 (Extended Unique Identifier) - IPv6 global unicast
Multi-layer switches operate at Data-link layer 2 and Network layer 3 layers
Hub operate at this level - pass info to everyone on network
Bridges operate at this level - point to point

Driver
Ethernet settings
Network and Sharing Center
Change adapter settings
Network Connections
Right click Ethernet - Properties - Configure
Driver
Driver Details - Make
 the LLC sublayer is implemented in the driver of the interface. The LLC takes care of the error-free transfer of data frames from one node to the other.

 cmd
-Viewing the MAC address of machine

ipconfig /all

Ethernet adapter Ethernet
Physical Address = MAC address of machine

-There are several protocols that function at the Data Link layer. One of these is the Address Resolution Protocol (ARP). This protocol determines the MAC address that corresponds to the appropriate IP address.

arp -a
 - shows arp table with corresponding MAC addresses

Network layer-
 IP addressing / Routing
PDU/Protocol Data Unit - Packets, Segment of data.
examine components of the Network layer of the OSI model. These components include the IP address, subnet mask, and default gateway for a device. Configuration details of the IPv4 and IPv6 protocols are a part of the Network layer.
IP addresses are logical addresses mapped to a physical component
Routers work at this level - Sometimes called layer 3 switch - Moves data across networks
Responsible for routing and IP addressing
Multi-layer switches operate at Data-link layer 2 and Network layer 3 layers


 ipconfig /all
View IPv4 address - The IPv4 address is a private IP address and can only be used on internal networks (not on the Internet)
Subnet Mask -   indicates that the range of IP addresses in the same subnet are from
Default gateway -

Change Network layer addresses
Right click internet on task bar
Open Network and Internet settings
Ethernet settings
Network and Sharing Center
Change adapter settings
Click Ethernet 2 link
Properties
Select Internet Protocol Version 4 (TCP/IPv4)
Properties
Here you can change IP address, Subnet mask, Default gateway

--check ipconfig /all for changes

Transport layer-
TCP/UCP for management and sending of our data
Flow control take place at this level

Error detection and recovery take place at this layer

PDU/Protocol Data Unit - Segment or Datagram
Protocols operating at the Transport layer include netstat and UDP

Netstat - This command lists the TCP sessions currently running on the device.

Cmd
netstat
View all TCP sessions currently running on the device

 create a new TCP session navigate to
https://www.comptia.org

netstat
Make note of new TCP sessions running
Under foreign address - Intranet HTTP

netstat -p udp
View all the services using UDP - DHCP, DNS, SNMP

Session Layer-
Provides connection management. Handshake, initiation, maintaining, who talks when
This layer establishes, maintains, and terminates communications between applications located on different devices
The session layer provides mechanism to open, close and manage communication session between end-user applications. Communication sessions consist of requests and responses between applications.
NFS/Network File system

Presentation Layer-
Formats data so it can be sent over a network, standardized or encrypted, or when received are formatting it so we can read it/put on computer and understand it
Protocols - referring to presenting file types to the user , audio, visual, text etc

The presentation layer is responsible for formatting and delivering information to the application for further processing or display. It relieves the application layer of concern regarding syntactical differences in data representation within the end-user systems.
Encryption device operates at this level - Formats data

Examples of these layers functioning within the Windows environment include the use of NetBIOS names for the Session layer and character code translation such as from ASCII to EDCDIC and back.

For the most part these functionalities cannot be directly viewed within a Windows environment as most Windows network components are structured around the TCP/IP model and as such, these layers are included within the Application layer.

Application Layer-
Different protocols that manage how applications are allowed to send and receive over the network.
They manage how data is able to create sessions and use resources
Allows our application  communicate with our network
HTTP, POP#3 SMTP

Ethernet
Windows Firewall link
Advanced settings
Windows defender firewall with advanced security
Right pane - inbound rules
Middle pane- These are network-aware applications that service the user applications utilized by the person operating the device.
Core Networking - Dynamic Host Configuration Protocol (DHCP-In)
Remote Desktop - User Mode
SNMP
Cast to Device streaming server (HTTP-Streaming-In)

Task manager
More details
Processes pane
Windows processes
Service host process -
that this process is running for the DNS Client, Network Location Awareness, as well as the Hyper-V Remote Desktop Virtualization Service. All these are network applications and services that require this process to run.

This process runs just below the network-aware applications such as web browsers, email clients, Remote Desktop clients, and other such software packages. This is the Application layer of the OSI model in action.