Friday, May 6, 2011

what happens when you type in a URL in browser

  1. browser checks cache; if requested object is in cache and is fresh, skip to #9
  2. browser asks OS for server IP address
  3. OS makes a DNS lookup and replies to browser
  4. browser opens a TCP connection to server (this step is much more complex with HTTPS)
  5. browser sends the HTTP request through 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, authorization request, etc.; this is handled differently from normal responses
  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