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The Internet & The Web

1. The Internet​

Resources: The following are helpful videos to help you understand the basics of how the Internet works:

The Internet is a large network of computers that communicate together.

  • Everything that is connected to the Internet, whether a server, a computer, a mobile phone, anything, is identified by an IP address, an unique string of numbers. Thanks to the unique IP address, any information you send or receive will reach the precise destination without getting lost and end up on someone else's device.

  • Because the network of computers can get complicated, anywhere that two or more parts of the Internet intersects, there exists a router, which directs the request and makes sure that a message sent from one computer arrives at the right destination computer.

To send a message to computer B, computer A must send the message to the router, which in turn forwards the message to computer B and makes sure the message is not delivered to computer C.

2. The Web​

Resources

Terms​

  1. Web Page: a document which can be displayed in a web browser.
  2. Website: a collection of web pages which a grouped together and usually connected together.
  3. Web server: a hardware/software that stores, processes (hosts) a website on the Internet.
  4. Search engine: a web service that helps you find other web pages: Google, Bing, Yahoo, DuckDuckGo. Search engines are access through a web browser (Firefox, Chrome, etc.) or a web page (bing.com, duckduckgo.com)

You open Chrome (web browser) and goes to Google (search engine). You type in "The New York Times", and Google takes you to "The New York Times" website. This website is hosted on a web server. You press on an article on "The New York Times" site, and it takes you to a web page of that article.

  1. Packets: when data is sent across the web, it's sent in thousands of small chunks (packets) instead of a whole big chunk of data. They’re broken down into these smaller chunks for two key reasons:
    • Efficiency: smaller chunks are faster to transmit. In case of error, it’s faster to replace small chunks than to replace the whole packet.
    • Routing: The header in each chunk guides them through the internet's complex network of routers, ensuring they reach the correct destination efficiently.

Each chunk of data after broken down (packet) has its own header, think of it as each page in a book having its own page number. Packet headers are like address labels and instructions for data to travel across the internet. They usually contain information such as:

  • Source and destination addresses: Tells routers where to send and deliver the data.
  • Protocol: Specifies the language the data speaks (e.g., HTTP for browsing, email).
  • Type of data: Identifies the content (e.g., text, image, video).
  • Other info: Additional details like sequence numbers, error checking, and more.

Example:​

  1. You open your home computer's web browser and type google.com (the domain name) into the address bar, initiating a request to access Google.
  2. Your browser (a client) sends a request to DNS server to obtain the IP address associated with google.com. The DNS server then returns the IP address corresponding to google.com back to your browser (142.250.181.230).
  3. Your browser then uses the obtained IP address to then create your request and other information. Your request then gets broken down to smaller chunks called packets, each of these packets has a header containing information such as:
  • Source IP address: your computer’s unique address on the Internet.
  • Destination IP address: the IP address of the Google server you’re trying to reach.
  • Protocol: what type of communication is used (eg: HTTP for web browsing).
  • The request method: (GET, POST, etc,…) depending on your action.
  • Other data: additional information specific to your request.
  1. The small chunks data travels through your home network (possibly using radio waves) to your Internet Service Provider (ISP) router. Here, they enter the internet backbone which are high-speed cables (fiber optic cables, undersea cables, wireless networks). This router reads the header on each chunk of data and direct the data chunks to their correct destination (the Google server), using different paths based on network traffic.
  2. The servers at Google's data center which hosts the google.com website then receives all the chunks, reassembles them into the original request, then processes it. It then creates sends back the requested data the way it came in, through the global network infrastructure (which are the high-speed cables mentioned earlier).
  • The software actors on the server side that take request, perform the processing, searching, computing, and provide the final response are called[[Module 1 - Cloud Concepts Overview#1. Web Services| web services]].
  • Web services use standardized protocols (like HTTP and SOAP) to communicate with your browser and exchange data.
  1. The data travels through the physical cables and arrives at your Internet Service Provider (ISP) router. The ISP then routes the data back to to your home wifi router, and the requested data reaches your home computer. → the requested data came back the way they went.
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