Computer Science – The internet and its uses | e-Consult
The internet and its uses (1 questions)
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When a user enters a URL (e.g., www.example.com) into a web browser, the following steps occur:
- URL Parsing: The browser first parses the URL to identify its components, including the protocol (e.g., HTTP), the domain name (e.g., example.com), and the path (e.g., /index.html).
- DNS Lookup: The browser uses the Domain Name System (DNS) to translate the domain name into an IP address. It first checks its cache, then queries a DNS server. The DNS server recursively queries other DNS servers until it finds the IP address associated with the domain name. This IP address is a numerical address that identifies the server hosting the website.
- TCP Connection: The browser establishes a Transmission Control Protocol (TCP) connection with the web server at the IP address obtained from the DNS lookup. TCP ensures reliable data transmission. A three-way handshake is used to establish the connection.
- HTTP Request: The browser sends an HTTP request to the web server. This request specifies the desired resource (e.g., /index.html) and the HTTP method (e.g., GET). The request includes information about the browser (User-Agent) and any cookies.
- Server Response: The web server receives the HTTP request and processes it. It then sends an HTTP response back to the browser. This response includes the requested resource (e.g., the HTML code of index.html), along with HTTP headers that provide information about the response (e.g., content type).
- Rendering Engine: The browser's rendering engine (e.g., Blink in Chrome, Gecko in Firefox) receives the HTTP response. It parses the HTML code, builds the Document Object Model (DOM), and then creates the Composite View Tree (CVT). The CVT represents the visual structure of the web page.
- Layout and Painting: The rendering engine calculates the layout of the page based on the CSS rules and then paints the page on the screen. This involves calculating the position and size of each element and drawing it on the screen.