Behind the scenes of Internet

The advent of computers made all life and work easier. When it comes to a large number of pages, most of the pages are written in the same language (HTML) and delivered using the same protocol (HTTP). HTTP is a commonly used Internet language or protocol (standard), which allows friendly conversations between machines running Windows systems and machines running Linux. The web browser can interpret the HTTP protocol and render HTML into the form of artificial prototypes. Web pages written in HTML can be browsed anywhere, with computers, mobile phones, Pads, and even popular game consoles. Even if you use the same language, different devices need to agree on certain rules when communicating through the web, just like you have to raise your hand when you ask questions in class (I guess not so much now with Zoom classes). HTTP is the protocol used for communication in the Internet. Due to the existence of HTTP, the client (just like computer) will know that it needs to request a Web page firs and send this HTTP request to the server. The server is the computer specified by the URL. The server receives the request, then finds the web page you want, and then sends it back to the computer (client) and display it in the browser.

Each request/response starts by redirecting URL in the browser address, like http://www.google.com. For instance, open the browser like Chrome and enter http://www. google.com. Click Enter and you will come to the Google’s homepage. One thing you may not know now is that the browser does not actually use URL to request web pages from the server but uses Internet Protocol or IP address. It is like phone number or postal code as it’s used as an identification server, not an actual phone or address. Google’s IP address is 173.194.203.106. You can open a new browser tab or new window, enter 173.194.203.106 in the address bar, and then click Enter. Now you will open the same web page as when you just entered http://www.google.com. This is because people are generally better at remembering words than a long list of numbers. Realizing this process is the DNS system, which is equivalent to the dynamic directory of all machines connected to the Internet. When you type http://www.google.com and press Enter, this address will be connected to its corresponding IP address. Since tens of millions of machines are connected to the Internet, not every DNS server can contain a list of all machines connected to the network. So there will be a system that will allow your request to be sent from this server to another server when the server cannot find what you want. Therefore, after the DNS system sees the URL of Google official website, it finds that it is located at 173.194.203.106, and then sends this IP address to your browser. Then, your browser will send a request to the server of this IP address and wait for a reply. If the whole process is normal, the server will send a message to the client (your browser) saying that everything is OK and then send the web page you want. The information sent is contained in the HTTP header.

 

References:

Martin Irvine, Intro to the Web: Extensible Design Principles and “Appification”
Ron White, “How the World Wide Web Works.” From: How Computers Work. 9th ed. Que Publishing, 2007. P. 3