HCI 201

Multimedia and The World Wide Web

The Internet

History of Internet

Started 1960s - Packet SwitchingResearch project by

U.S. Department of DefenseARPAnet

(Advanced Research Projects Agency)Really took off in 1993

History of the World Wide Web CERN (Tim Berners-Lee)

developed authoring language and distribution system for creating and sharing multimedia-enabled, integrated electronic documents over the Internet

World Wide Web and HTML was born

Allows relationships between documents and elements

NCSA developed Mosaic to view these documents

Overview

The Internet The WWWHow does it all work?

Hardware Software Networking Protocols

Internet and World Wide Web

What’s the difference between the two terms?

The Internet and the WWW

The Internet (late 60s): “It’s a worldwide collection of computer networks – a network of networks – sharing digital information via a common set of networking and software protocols.” HTML & XHTML – The Definitive Guide

The World Wide Web (early 90s): the monster application that runs on the Internet infrastructure (over 2 billion pages). With the invention of GUI -> color, voice and video were

added to the Internet.

History of the Internet

Started 1960s - Packet SwitchingResearch project by

U.S. Department of DefenseARPAnet

(Advanced Research Projects Agency)Really took off in 1993, why?

http://www.isoc.org/internet/history/ URL

History of the World Wide Web

CERN (Tim Berners-Lee) developed authoring language and distribution system for creating and sharing multimedia-enabled, integrated electronic documents over the Internet

World Wide Web and HTML was born. Allows relationships between documents and

elements. NCSA developed Mosaic to view these docs.

http://www.isoc.org/internet/history/ URL

Overview

The Internet The WWWHow does it all work?

Hardware Software Networking Protocols

Hardware

The difference between hardware and software is you can touch hardware.

The hardware you need to be connected to the Internet is A computer A networking device, e.g. a modem or network card A connection, e.g.

At home, an Internet Service Provider At school, a LAN connection

Telephone (Dial-Up) Modem: Low Speed but Inexpensive & Widely Available

Modem - device that sends and receives data over telephone lines to and from computers

Most modems today have a maximum speed of 56 Kbps.

Internet Service Provider (ISP)

ISP - a company that connects you through your communications line to its servers, or central computer, which connect you to the Internet via another company’s network access points

Software

Software is a term used to describe programs that allow the hardware to do things for you.

You need a few pieces of software to connect to the Internet An operating system, e.g. Windows XP A browser, e.g. Internet Explorer, Firefox, Opera

If you want to develop web sites or pages, you need a few more Authoring tool, e.g. Notepad, Dreamweaver or Frontpage FTP program, to transfer files from your client machine (in

front of you) to the server (your students account), e.g. SSH

Protocols

Because networks use a wide variety of hardware and software, protocols are needed to coordinate communication and data transmission.

A protocol is a set of rules for the exchange of data across communication lines.

Protocols make the whole thing work!

Standards Organizations

World Wide Web Consortium (W3C)Internet Engineering Task Force (IETF)

http://www.w3c.org

http://www.ietf.org

URL

What protocols doIdentify the different devices in the

communication path.Establish the speed and method for

transmission of data.Alert the receiving device to the incoming data.Determine the method of error checking and

correction.

HyperText Transfer Protocol

HTTP is the protocol responsible for transferring and displaying web pages.

HTTP uses the client/server model of computing. The client is the user’s web browser:

a software program that retrieves the page and displays it. (I.E, Netscape). A Web browser can either be text-based, or graphical.

A Web page is stored on a Web server, which makes the page available to users of the Web.

The server is the web server where the page resides. (Ex: www.nyt.com)

TCP/IP protocol

TCP – Transmission Control Processing IP – Internet Protocol

TCP: Rules to control on how messages are broken down into packets, and then reassembled at the final destination.

IP: Rules to label packets for delivery and to control the packet’s path from sender to recipient.

TCP/IP software processes data transmission through the Internet.

Internet protocols

Simple Mail Transfer Protocol (SMTP): transferring email messages from one machine to another

File Transfer Protocol (FTP): transferring files between local and remote machines.

Telnet: a terminal emulation protocol used to remote login.

Others?

TCP/IP

HTTP

POP

IP addresses: dotted quads

Each node in the IP world is identified by a unique 32-bit number called an IP address.

IP addresses appear as a series of four 8-bit numbers separated by dots (dotted quads). Each number ranges from 0 to 255.14.192.1.100 students.cs.depaul.edu

IP addresses are usually assigned human-readable names (domain names).

IP Address

126.12.1.7

126.1.1.1

126.12.1.1

126.12.1.2126.12.1.3

126.12.1.4

126.12.1.5126.12.1.6

15.35.200.1

15.35.200.2

15.35.200.3

132.12.1.6

132.12.1.5

132.12.1.4

132.12.1.3

132.12.1.2

132.12.1.7

132.12.1.1 245.12.50.5

245.12.50.6

245.12.50.7

245.12.50.8

245.12.50.9

152.123.200.1

152.124.20.2

152.124.20.3

152.124.20.4

152.124.20.5

152.124.20.6152.124.20.7

152.124.20.8

146.182.0.1

146.182.0.2

146.182.0.3

146.182.0.4

146.182.0.5

146.182.0.6

146.182.0.7

146.182.5.5145.12.50.1

172.11.11.1

172.11.11.2

172.11.11.3

172.11.11.4172.11.11.5

172.11.11.6

172.11.11.7

172.11.11.8

172.11.11.9

172.11.11.10

172.11.11.11

172.11.11.12

172.11.11.13

172.11.11.14

172.11.11.15

172.11.11.16

Domain Name Server (DNS)

www.yahoo.com(Domain Name)

64.58.76.223(IP Address)

IP addresses are hard to remember.

amazon.com

yahoo.com

microsoft.com

depaul.edu

chicago.com

news.com

cnn.com

Domain

Amazon. COM

yahoo.com

microsoft.com

depaul.edu

chicago.com

news.com

cnn.com

Domain Name

www.yahoo.com

www.cti.depaul.edu

www.depaul.edu

www.chicago.com

www.microsoft.com

Domain Name Server

A Domain Name Server is responsible for the mapping between domain names and IP addresses.

bach.cs.depaul.edu

Org. type (top level domain)

Organization name

Organization name

Host name

IP address: 140.192.33.6

.com

.org

.gov

.mil

.net

.fr

.museum

.biz

A Typical HTTP Exchange

Client: Please open a connectionto ‘www.nytimes.com’ and send methe default file. I am located at IP Address 140.192.1.6.

Netscape’s URL Window

NY TimesWeb Server

Server: Let me check…. Okay, the default file at this site is of type HTML. It is 1749 bytes in size. Thedate is Tue, May 2nd at 15:33:33.

NY Times Web Page

Web Pages and Web Browsers

A Web page is stored on a Web server, which makes the page available to users of the Web.

To view a Web page, the user runs a Web browser, a software program that retrieves the page and displays it.

A Web browser can either be text-based, or graphical.

URL: Uniform Resource Locator• People on the Web use a naming convention

called the uniform resource locator (URL).

• A URL consists of at least two and as many as four parts.

• A simple two part URL contains the protocol used to access the resource followed by the location of the resource.

Example: http://www.cs.depaul.edu/

• A more complex URL may have a file name and a path where the file can be found.

http://facweb.cs.depaul.edu/aburns/research/res_interests.html

domainThe protocol

used path that indicates the location of the document in the host’s file system

documentname

A Web URL deconstructed

The user is a directory in the system

aburns @ cs . depaul . edu

HandleHost/Server Domain

Top leveldomain

Others:• students• hawk• condor

Others:• com, net, org,• mil, gov• fr, uk, dz• info, biz, name,pro, museum, coop

Anatomy of an e-mail address