Notes

SSH key-based authentication allows you to generate a public/private key. Place the public key on the server you are trying to access and the private key is kept with you on your machine. When you SSH to the server from the machine which has the private key , the server will immediately logs you in.

Introduction

Computer Networks is a communication network established between many electronic devices, not necessarily computers only for sharing resources and data. Such a network is established using physical links (such as cables, fiber, etc.) or can be wireless. (Wi-Fi, Bluetooth, etc.).

Open system is a system that is connected to the network and is ready for communication.

Closed system is system that is not connected to the network and can’t be communicated with.

Transmission Modes determine how data is transferred between two devices in a computer network. There are 3 transmission modes in computer networks:

• Simplex Communication is uni-directional or one-way in Simplex Mode. i.e. Only one device is allowed to transfer data and the other device simply recieves it. e.g. Radio Station (The station transmits and the radio only recieves).

• Half-Duplex Communication is possible both-ways but not simultaneously. i.e. Both the devices/stations can transmit and recieve data but not at the same time. At an instant, only communication in a single direction is allowed. e.g. Walkie-Talkie.

• Full-Duplex Bidirectional communication is possible simultaneously. This can be possible in the following cases:

  • Dedicated seperate channels for transmission and reception
  • Capacity is divided between transmission and reception (if single channel is used)

  e.g. Cellular/Telephone Network.

PAN, LAN, WLAN MAN, WAN, GAN

History Lesson: Revisiting Networking Stone Age

https://www.youtube.com/watch?v=CRdL1PcherM&list=PLIhvC56v63IJVXv0GJcl9vO5Z6znCVb1P&index=4

OSI (Open Systems Interconnection) Model

The OSI (Open System Interconnection) reference model is a comprehensive set of standards and rules for hardware manufacturers and software developers. By following these standards, they can build networking components and software applications that work in any environment.

It provides a framework for creating and implementing networking standards, devices, and internetworking schemes. It explains the networking from a modular perspective, making it easier to understand and troubleshoot.

Motivation:

• To build agnostic applications
  • Without a standard model, your application must have knowledge of the underlying network medium imagine if you have to author different version of your apps so that it works on wifi vs ethernet vs LTE vs fiber.
• Network Equipment Management
  • Without a standard model, upgrading network equipments becomes difficult.