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
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):
- browser checks cache; if requested object is in cache and is fresh, skip to #9
- browser asks OS for server’s IP address
- OS makes a DNS lookup and replies the IP address to the browser
- browser opens a TCP connection to server (this step is much more complex with HTTPS)
- browser sends the HTTP request through TCP connection
- browser receives HTTP response and may close the TCP connection, or reuse it for another request
- 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)
- if cacheable, response is stored in cache
- browser decodes response (e.g. if it’s gzipped)
- browser determines what to do with response (e.g. is it a HTML page, is it an image, is it a sound clip?)
- 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
http://www.inetdaemon.com/tutorials/internet/tcp/3-way_handshake.shtml
xiangcaohello 