How Does the Internet Work

1
How Does the Internet Work?

• Spring 2009

2
What is the Internet?

• The Internet involves millions of computers,
  connected in complex ways to a maze of local and
  regional networks
• Network of Networks
• Capital I in Internet

3
Origins of the Internet

• 1969
• Department of Defense established experimental
  network connecting 4 research computers
• Called ARPANET
• 1980s National Science Foundation involved
• Only scientific, research and academic
  institutions (no commercial traffic)

4
Other Developments

• 1989 - E-mail connectivity thru CompuServe and
  MCI Mail (restrictions lifted)
• 1991 move towards private sector
• Network Access Points (NAPs)
• Now called Internet Exchange Points (IXPs)
• Internet Service Providers (ISPs)
• Companies that connect users to Internet
• Verizon, ATT, Comcast, AOL, NetZero, etc.
• Communication coordinated through national and
  international organizations (standards)

5
Connect to Internet

• Ways to connect
• Dial-up
• Broadband
• DSL (Digital Subscriber Service)
• Cable Modem
• Fiber-Optic Internet (Verizon)
• Satellite (via a dish)
• ISP Internet Service Provider
• Find one at www.thelist.com
• Individual users enter ISP through a POP (point
  of presence) bank of modems
• ISPs maintain multiple POPs for geographic area
  they serve

6
Who Owns the Internet?

• No one company or country can be considered as
  owner of Internet
• Ownership shared among various entities
• Coordination
• Internet Society (ISOC)
• Internet Engineering Task Force (IETF)
• Internet Architecture Board (IAB)
• World Wide Web Consortium (W3C)
• In the US
• ICANN Internet names and port numbers

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ICANN

• Internet Corporation for Assigned Names and
  Number
• Founded in 1998
• ICANN now reports to U.S. Commerce Department
• Controls addresses such as .com and country
  domain names such as .cn for China
• U.S. will probably allow ICANN to become
  independent by 2009 (end of agreement)
• June 2008 New Top-Level Domain Names now
  possible starting 2009 (but )
• .paris, .nyc, .berlin, .love, etc.
• ICANN Announcement 2008
• InfoWorld ICANN Article 2008

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Difference Between Internet and Web?

• World Wide Web is just one of the services
  deployed on the Internet
• Subnetwork
• Linked documents, use of HTML
• Early 1990s First browser (graphics with text)
• Mosaic ? Netscape
• Other services deployed on the Internet include
• E-mail, FTP, IM, P2P, Telnet, etc.

http//netforbeginners.about.com/cs/technoglossary
/f/Faq1.htm
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What is Internet2?

• Consortium of over 200 universities
• Works with industry and government
• Internet2 develops and deploys advance network
  applications and technologies for research and
  higher education
• 3D imaging (medical field)
• Videoconferencing
• Remote access to Electron Microscope (Lehigh) for
  K-12
• ABILENE high-performance network
• 10 Gigabit Internet2 Backbone
• Dec. 2005 U of S becomes participant through
  MAGPI
• Mid-Atlantic GigaPop in Philadelphia for
  Internet2
• University of Scranton - Internet2

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Internet Address

• Each computer connected to the Internet has a
• unique number or address identifying it
• IP Number/Address 32-bit address
  (4 part decimal )
• 134.198.10.10 University of Scranton
• 134.198.168.1 Comp. Sciences
• 134.198.168.8 CS Literacy Server
• Domain Name
• Logical name for computing system
• www.scranton.edu
• Top-Level Domain (suffix)
• ICANN

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Find a Web Page?

• Your computer will contact a Domain Name Server
  (local)
• www.cs.scranton.edu 134.198.168.1
• Network Information Server (wider area)
• Maintain databases with domain names and IP
  numbers in binary format
• Domain Name
• ?
• IP Number (logical)
• ?
• Ethernet Address (physical - network card)
• or
• MAC (Media Access Control) Address (48-bit
  Address)
• How to Find Your MAC address

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IP ADdress

• IP Address changes as you connect to the Internet
  via different network
• University of Scranton
• Home (Verizon DSL)
• FYI - Linksys Router (home network) 192.168.1.1
  (default)
• Showipaddress.com site
• WHOIS IP
• WHO (scranton.edu)

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Desktop/Laptop

• Static IP address
• Specified manually and entered into network
  tables
• Permanent address
• Mostly for file servers
• Dynamic IP address
• Dynamic Host Configuration Protocol (DHCP)
• Ask network for an IP address when you turn it on
  (from a pool of available addresses)
• IP address changes each time computer is used
• Mostly for Clients (users)
• My IP address at home 71.181.178.???

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Web Browsers

• Internet Explorer, Mozilla FireFox, Netscape
  Navigator, Opera, Apple Safari
• System of communicating Web documents
• Hypertext Transfer Protocol (HTTP)
• Protocol used to transfer Web pages
• Formatting instructions called
• HTML (Hypertext Markup Language)

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HTML Tags

• Begin/End of document
• Bold
• Paragraph
• Title top of
  window
• Use in tabular form
• Ordered List
• 
  Break (new line)
• Image

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JavaScript for Interactivity

• Allows for local processing (on your machine)
  instead of on server (server-side processing)
• Browser handles some processing chores before
  transmitting to server
• Client-Side Processing
• Buttons, Check boxes, drop-down lists
• Error-checking
• Advantage
• Faster response to user interaction
• Disadvantage
• Opens user to possible risks (exploit weakness in
  browser)

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JavaScript Example

• / This script and many more are available free
  online at
• The JavaScript Source!! http//javascript.internet
  .com
• Created by Lee Underwood http//javascript.inte
  rnet.com/ /
• var agree0 // 0 'no', 1 'yes'
• agree2()
• function if (!document.getElementById) return
  false
• agree1
• document.getElementById('box').style.background
  'fff000'
• if (agree)
• document.getElementById('enterName').style.vis
  ibility 'visible'
• document.enableform.box.focus()
• function disagree()
• if (!document.getElementById) return false
• agree0
• if (!agree)

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Terms Internet

• ABILENE (Internet2)
• ARPANET (Dept of Defense)
• Cable-modem
• Client-side processing
• Dial-up
• DSL
• Domain name
• DHCP
• Domain Name Server
• Dynamic IP address
• Fiber-Optic
• HTML
• HTTP

• ICANN (2009)
• ISP
• IP Number / IP Address
• Internet2
• JavaScript
• MAC address
• MAGPI
• Mosaic / Netscape
• National Science Foundation
• POP
• Satellite
• Server-side processing
• Static IP address
• Top-level domain
• WEB BROWSER
• World Wide Web Consortium