WebFund 2016W Lecture 3

Video

The video from the lecture given on January 14, 2015 is now available.

Notes

In-class Notes

Lecture 3
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What is the web?

Web != Internet

So, what is the Internet?!

Network of networks

What is a network?

Networks allow computers to talk to each other

WiFi, Ethernet, LTE - different standards for computer networks

Layers of networking (OSI)
* Physical layer
* Data link layer
* Network layer <---- 
* Application layer (and such)

Internet Protocol (IP)
 - packet-based protocol (NOT a stream or continuous protocol)


Old POTS
 - wire from your house to a switching station
 - wires between switching stations A and B
 ...
 ...
 - wires between switching station Y to Z
 - wire from switching station to house

Packet switching networks multiplex physical wires over time. (Multiple communication connections over one wire by them taking turns.)

The "turn" is the packet

IP protocol is a "best effort" protocol. NO error correction or retransmission.

TCP means Transmission Control Protocol
turns packets into a reliable data data stream

Network Firewalls block "unwanted traffic"
 - really, block all those protocols that aren't safe on the open Internet

TCP adds a "port" to the IP address
 - the port identifies which program to talk to
 - some are ephemeral (temporary)
 - others are "well known", meaning protocol on that port is standardized

Port 25 is for SMTP (email)
80: HTTP
443: HTTPS
22: ssh


Web is transmitted over HTTP

Major HTTP commands
 * GET: get documents from server
  - can be CACHED
 * POST: send form contents to server
  - are not cached

You can GET almost anything
 - MS Word .doc
 - tiff
 - PDF

But the real web is
 - JPEG, GIF, PNG for images
 - CSS for style sheets
 - HTML for content
 - JavaScript for code

.swf is flash.  Flash is not a web standard.  AVOID