INP 160: Internet Technology

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INP 160 Internet Technology

• Class 14 Organizational Connection Options

2
Objectives

• What is VPN?
• What is a virtual domain?
• Describe bandwidth issues.
• What issues are involved with Internet connection
  points?
• What issues are involved with audience access?
• What are some issues involved with Internet
  Service Providers (ISP)?
• What issues are involved with connection types?
• What is a proxy server?

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Updates

• There are no classes next Monday, July 4th.
• Assignment 3 is due the July 18th.

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What is bandwidth?

• How much can a specific data channel transfer in
  a given unit of time?
• Frequency in Kbps or Mbps
• For example, an image that is 200k could travel
  over a 56k connection in approximately 60
  seconds
• How long would a 1 Mb take?
• http//www.numion.com/Calculators/Time.html

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MHz frequency

• What is frequency?
• How often something is repeated, or how many
  cycles per some unit of time
• Hertz (Hz) and Megahertz (MHz)
• Flickering images
• Processor
• Sine waves

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Internet Connectivity

• Below are types of interconnectivity roughly
  arranged by downstream speed
• Cellular access WAP
• SLIP/PPP
• DSL
• ADSL
• Cable
• Wireless

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Internet connectivity Desktop
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Internet Connectivity Wireless
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PPP/SLIP connections

• The clients computer modem directly interacts
  with server modem
• ISPs have thousands of modems to receive incoming
  requests
• Can transfer up to 56 kbps (typically 45 kbps)

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AT command set

• Created in 1981
• How a modem makes a connection
• Caught on because Hayes Smartmodem upgrade from
  1200 to 2400 was fast.
• Now a de facto standard
• Hayes originally sued all companies producing
  modems that claimed they were Hayes compatible,
  so called AT command set
• Attention, which precedes commands (e.g., ATD
  stands for Attention dial)

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Modems AT commands

• Modem goes off hook
• Opens a connection on phone line
• Dials a number to reach receiving modem
• Handshake is made
• What speed should the connection use?
• Any error checking

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Modems AT commands cont

• After handshake, data is sent digitally as binary
  code. e.g., 0010101001
• However, because telephone lines are analog,
  modems must modulate and demodulate.
• Modulate change from digital to analog
• Demodulate change from analog to digital
• Modem MOdulate/DEModulate

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Cable connections

• Uses cable modem
• Not a true modem does not have 11 relationship
  with another modem!
• Ethernet networking card connects computer to
  coaxial line
• Computer signals and television channels travel
  over a 6 MHz channel
• Cable usually has 330 450 MHz capacity

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Cable connections cont

• LAN (500 homes) share a connection
• Each LAN is connected by high-speed fiber optics
  line to head end
• Head end
• Cable facility, houses servers proxy servers
• Serve many LANs
• Internet Exchange Points (NAPs) with a PoP
• Also receive satellite transmissions of
  television channels

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Virtual Private Networks

• VPNs
• Offer a secure method to use an organizations
  network remotely
• Essentially encrypts messages so they are
  private, even though they travel over the
  Internet, which is public.
• As opposed to a private network, which has
  cables/circuits established physically to only a
  certain set of computers.
• Doesnt use Internet
• Remote access is impossible, hence the need for
  VPN

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How VPN works

• Two computers must have client software with
  encryption software
• Creates an encrypted tunnel, or a tunnel.
• Encrypted packets are placed within unencrypted
  packets, which are routed publicly through a
  tunnel using IP.

Source www.multitech.com
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How VPN works cont

• Routers are given IP address to destination
  network, not to destination.
• The tunnel travels over the Internet.
• Once packets reach LAN, the outer packet is
  discarded, and the inner packet is used to
  deliver the data.

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Virtual Domains

• What are virtual domains?
• Hosting multiple domains on a single server
  i.e., multiple domains share a single IP address
• Uses software instead of dedicated hardware
• Strengths
• Doesnt require personal server affordable
• Reduce no. of IP addresses needed
• Weaknesses
• Cannot create secure connection but proxy can
• Requires HTTP 1.1 or better, so old browsers can
  pose a problem

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Virtual Hosting

• Often provided by ISP
• Typically below 10/month with around 500 MB to
  10 GB
• Vary in support, e.g., CGI, PHP, MySQL, SSL

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Current bandwidth issues

• Streaming audio/video
• Solution offer a variety of streams varying in
  quality
• Images
• Solution optimizing images for the web
• Peer-to-peer file sharing
• Big problem for campuses!
• Sharing files eats up bandwidth
• Videoconferencing
• Solution 101 compression ratio is lossy, but
  can reasonably transfer up to 6 frames/second

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Bandwidth Issues

• Bandwidth issues dont just apply to
  Internet/networking
• Hard drives, floppy disks, CDs and DVDs, stand
  alone video games
• Response time drops as bandwidth goes up

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Bandwidth issues with ISPs

• Bandwidth shared for cable users in LAN
• Limited number of modems for SLIP/PPP connections

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ISPs, censorship and user tracking

• ISPs often censor illegal activities, but what
  else?
• E.g., Comcast
• Comcast cable refused to air anti-war cable ads
  and referred to them as unsubstantiated

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Audience Access

• Web is unique in that any individual can produce
  web material to is nearly immediately accessible
  to a broad audience.

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Issues of audience access

• Regulating what kids can access online
• E.g., filtering software like Net Nanny
• Also, regulating what library patrons can access,
  what primary school students can access, etc.
• Accessibility for individuals with disabilities
  using assistive technology AT.
• Sorry, two ATs in one day.
• Age verification systems
• Usually involve credit card
• Affects privacy, especially identity theft

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Discussion filtering

• What are some issues with filtering software,
  especially for schools and children?

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Review

• What is bandwidth?
• What is frequency, as measure in Hz?
• Internet connections approximate speeds
• What are modems, and how do they work? Modulate
  and demodulate
• How do cable connections work?
• How does VPN work? Whats a tunnel?
• What are virtual domains and virtual hosting?
• What are some common bandwidth issues?
• What are some connectivity problems with ISPs.
• What are some issues with addressing audience
  access?