Web Cache and HTTP

Caching Tutorial for Web Authors and Webmasters

https://www.mnot.net/cache_docs/#SCRIPT

HTTP Made Really Easy
A Practical Guide to Writing Clients and Servers
http://www.jmarshall.com/easy/http/

 

http://stackoverflow.com/questions/2092527/what-happens-when-you-type-in-a-url-in-browser

http://www.quora.com/Programming-Interviews/What-happens-when-you-type-google-com-into-your-browsers-address-bar

In an extremely rough and simplified sketch, assuming the simplest possible HTTP request, no proxies and IPv4 (this would work similarly for IPv6-only client, but I have yet to see such workstation):

  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.).

 

TCP 3-Way Handshake

TCP 3-Way Handshake
TCP 3-Way Handshake
TCP 3-Way Handshake

http://www.inetdaemon.com/tutorials/internet/tcp/3-way_handshake.shtml

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s