Understanding URLs and Internet Communication

Study Notes

Information from URL Summary

URLs (Uniform Resource Locators) are unique addresses used to identify resources on the internet. These resources can range from web pages and images to videos and files. When you enter a URL into your browser's address bar and hit 'Enter', your computer sends a request to the server where the resource is located, asking it to send back the information associated with that URL. This process involves several steps, including domain name resolution, TCP handshake, HTTP request, and HTML rendering. In this article, we will focus on understanding what happens when you visit a URL and how the information from the URL is processed by your browser.

Understanding URL Components

A typical URL consists of various components, which include protocol (e.g., http://www.example.comdomain name (e.g., example.com), path (e.g., /path/to/file), query string (e.g., ?param=value), and anchor (e.g., #fragment). While all these parts may seem necessary, not every URL will contain each element. For instance, some URLs may only include the protocol and domain name, such as http://www.example.com. Other URLs might have more complex structures, like https://www.example.com/products?color=blue&size=medium#reviews.

The protocol part specifies the communication method between your browser and the server hosting the requested resource. The most common protocols are HTTP (Hypertext Transfer Protocol) and HTTPS (HTTP Secure), which are used for transferring data over the internet.

The domain name is a part of the URL that identifies the server or organization that hosts the resource. The domain name is separated into parts using dots (.), with the main part being the top-level domain (TLD) such as .com or .org.

The path is the part of the URL that specifies the location of the requested resource on the server. It can include directories and specific files.

The query string is used to pass additional information to the server. This information can be used to customize the response based on the user's request. For example, a search engine might use the query string to determine which results to display.

The anchor is used to link to a specific part of the page. It starts with a # symbol followed by a unique identifier.

DNS Lookup

When you enter a URL into your browser, the first step is to perform a DNS lookup. DNS stands for Domain Name System, and it's responsible for translating human-readable domain names into the numerical IP addresses that computers use to identify each other on the internet.

Your browser sends a request to a DNS server for the IP address associated with the domain name in the URL. If the domain name is registered, the DNS server will return the corresponding IP address.

TCP Handshake

Once the browser has the IP address, it sends a TCP (Transmission Control Protocol) handshake request to the server. The purpose of this handshake is to establish a connection between the browser and the server. The TCP connection is established by following these steps:

The client sends a SYN (synchronize) packet to the server.
The server responds with a SYN/ACK (synchronize/acknowledge) packet.
The client sends an ACK (acknowledge) packet to the server.

HTTP Request

After the TCP connection is established, the browser sends an HTTP (Hypertext Transfer Protocol) request to the server. The request includes details such as the requested resource, the method (e.g., GET or POST), and any additional data provided in the query string.

HTML Rendering

Once the server has received the HTTP request, it processes it and sends back an HTTP response. The response usually includes the requested resource (e.g., web page, image, or file) in the form of HTML (Hypertext Markup Language) code. The browser then renders this HTML code, displaying the requested resource to the user.

Conclusion

In conclusion, when you visit a URL, your browser goes through a series of steps to retrieve and display the information associated with that URL. These steps include DNS lookup, TCP handshake, HTTP request, and HTML rendering. Understanding this process helps you appreciate the complexities involved in accessing resources on the internet.

Description

Learn about the components of a URL, the process involved when visiting a URL, and the communication steps between your browser and the server. Gain insights into DNS lookup, TCP handshake, HTTP requests, and HTML rendering.