Day 1 Notes - owenkelly14/Net150 GitHub Wiki

DAY 1:

OSI Model (Open Systems Interconnection) - 7 layers

7: Application - The data the computer is receiving

6: Presentation - Compression, encrypting and other encoding

5: Session - Session set up and session teardown (session

4: Transport - Port numbers tell the receiver what application the data is for. Port 80 - HTTP web traffic | Port 25 - SMTP email | Port 22 - SSH

3: Network - IP addresses of sender and receiver

2: Datalink - Defines how packets get onto the media (prevent collisions & are they ready?)

1: Physical - Physically send the bits of media (copper wire, fiber optic, radio waves)

Sessions are a temporary, interactive exchange of information between two or more devices that are communicating over a network

OSI helps locate problems, manage complexity and concentrate on one aspect of communication at a time

TCP - Used for applications that prioritize data integrity, such as reliable delivery and congestion control UDP - Used for short transfers, such as HTTP redirection, to minimize TCP overhead

Each layer can add or remove information on the packet to help to know where it should go next