Understanding the OSI Model

OSI Model is the original model on which the TCP/IP Model was based upon
It has 7 layers

Data in OSI Model passes from layer 7 to layer 1 at sender's side and from layer 1 to layer 7 at receiver's side

1. Appication Layer

Provides an interactive interface for user to enter and view data
One can give inputs in the form of text, audio, img, files, etc.
Browser makes up the application layer

2. Presentation Layer

Data is converted into computer-friendly format(binary)
So, this layer encodes input, compresses it and encrypts it if required

3. Session layer

Initiates and creates sessions
Provides context to communicate netween devices

4. Transport Layer

Establishes application-level connectivity
Attaches source and detination port numbers
Performs error control, makes 'checklists' so that it can be cross-checked at receiver-end to ensure that all data is transferred properly and not destroyed on the way in between
These 'checklists' are known as 'checksums'
Known as the 'heart' of the networking

5. Network Layer

The source and destination IPs are attached here
Has network-level routing and pathing of packets for purpose of identification of devices and to decide virtual path that needs to be taken by data packets

6. Data-Link Layer

Attaches source and destination MAC Addresses, which are used to identify hardware information of a device
Calculates checksums for error checking of metadata that has been attached at all previous layers and also to manage data-flow

7. Physical Layer

This is where the data is converted into hardware friendly signals, radio signals, light signals, or electric signals depending on hardware that's being used for transfer

Trick to remember all 7-layers in OSI Model:

"All People Seem To Need Data Processing"