What happens when a URL is typed in a browser ??

Question

Somewhere in the internet I saw promiscuous mode of networking is used by hacker but is there any use case in which it becomes mandatory to change the mode of network interface in promiscuous mode ?

Answer 1

Here are the simplest steps followed :

1. Browser checks cache; if requested object is in cache and is fresh, skip to #9
2. Browser asks OS for server's IP address
3. OS makes a DNS lookup and replies the IP address to the browser
4. Browser opens a TCP connection to server (this step is much more complex with HTTPS)
5. Browser sends the HTTP request through TCP connection
6. Browser receives HTTP response and may close the TCP connection, or reuse it for another request
7. Browser checks if the response is a redirect (3xx result status codes), authorization request (401), error (4xx and 5xx), etc.; these are handled differently from normal responses (2xx)
8. If cacheable, response is stored in cache
9. Browser decodes response (e.g. if it's gzipped)
10. Browser determines what to do with response (e.g. is it a HTML page, is it an image, is it a sound clip?)
11. browser renders response, or offers a download dialog for unrecognized types

Again, discussion of each of these points have filled countless pages; take this as a starting point. Also, there are many other things happening in parallel to this (processing typed-in address, adding page to browser history, displaying progress to user, notifying plugins and extensions, rendering the page while it's downloading, pipelining, connection tracking for keep-alive, etc.).