How the Web Works

relies on a number of system, protocols and technologies working together in unison

protocol: a set of rules that partners use when they communicate

TCP / IP - layered architecture

applications layer

transport layer

internet layer

link layer

physical transmission of data

establishing logical links

MAC addresses

routes packets between partners

uses IP addresses

IPv4 and IPv6

ensures transmissions arrive in order and without error

broken into packets according to TCP

0.5 - 1k

header

ACK - acknowledges its successful arrival

process-to-process communication

HTTP

SSH

FTP

POP / IMAP / SMTP

DNS

DNS

hosts file

name levels

registration

address resolution

URL

protocol

TCP/IP stack

domain

ftp://example.com/abc.txt
http://example.com/abc.txt

port

identifies the server

path

a software connection point

folder on the server

query string

HTTP

TCP connection on port 80

headers

request headers

host

user agent

accept

accept-encoding

connection

cache-control

response headers

server

last-modified

content-length

content-type

content-encoding

request methods

GET

POST

PUT

DELETE

TRACE

OPTIONS

response codes

200: OK

300: Moved Permanently

304: Not Modified

307: Temporary redirect

400: Bad request

404: Not Found

401: Unauthorized

414: Request URI too long

500: Internal server error

browser

many HTTP requests and responses

rendering

caching

Web Servers

a computer that responds to HTTP requests

application stack

os, web server software, database, scripting language

LAMP, WISA, MEAN

apache / IIS

MySQL, DB2, Oracle

PHP, Python, ASP.NET