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Lecture_3_Notes.md

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How the Internet Works

1. Internet

⭐ What is Internet?

  • Internet is a global system where billions of devices & other resources are interconnected with each other.

  • Internet is a Global System/ Network of Networks

2. History of Internet

  • 1960 - ARPANET(The Advanced Research Projects Agency Network)

They want to send big file in the form of small packets in their destination.

  • 1970 - Organization using internet in big scale.
  • 1980 - DNS(Domain Name System)/WWW
  • 1990 - Commercial Websites, Email etc
  • 2000 - Facebook & Mobile Era.
  • Today - AI (We can do everything through Internet).

3. Need of Address

  • If you want to communicate with other machine you need an IP Address.

4. Client - Service Modal

  • The client–server model is a distributed application structure that partitions tasks or workloads between the providers (servers) and service requesters (clients). It is commonly used in computer applications such as email, network printing, and the World Wide Web.

5. Protocol Stack and Packets

  • Let's take an example if a one machine sending 100MB File to another machine it will be sended in the form of small packets and re-unite in the destination.
  • Protocol is a set of rules to follow
  • TCP defines PORT Number
  • IP will defines it address and added to Hardware.

6. How Packet travels?

  • Client wants to send request through a router then your ISP get the IP Address and recall itself that I know this IP Address, then it goes to server using multiple routers.

Let's learn this thing in more depth:

  • Three Layers of ISP:
    • Local ISP
    • Regional ISP
    • NSP (National Service Provider)

7. Router & Routing Table

  • Router: A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions between networks and on the global Internet

  • Routing Table: A routing table is a data table stored in a network host that lists the routes to particular network destinations, and in some cases, metrics (distances) associated with those routes.

8. Understand request for www.google.com

9. Protocols

  • Three layers of Protocols:

    • HTTP (Hypertext Transfer Protocol) is an application-layer protocol used for transmitting hypermedia documents such as HTML.

    • FTP (File Transfer Protocol) is a standard communication protocol used to transfer computer files from a server to a client on a computer network. It is built on a client-server model architecture using separate control and data connections between the client and the server.

    • SMTP (Simple Mail Transfer Protocol) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages.