Internet

1
Internet LAN Technology

• CSci 100

2
Overview

• History of the Internet
• The Internet backbone
• NAPs, NSPs, routers, and ISPs
• Ping and Traceroute
• TCP/IP
• IP Addresses and domain names
• Dial up connections and modems
• High speed Internet access
• Wireless Internet access

3
History of the Internet

• The United States created ARPA
• Advanced Research Projects Agency
• Helped scientists communicate and share valuable
  computer resources
• Response to Soviet Unions launch of Sputnik in
  1957, the first artificial satellite
• ARPANET, created in 1969, connected computers at
  four universities
• UCLA, Stanford, Univ. of Utah, UCSB

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ARPANET
5
How is the Internet structured?
6
How can I track data traveling over the Internet?

• Using Ping or Traceroute, you can discover how
  long data is in transit
• ping www.highline.edu
• tracert www.highline.edu
• High latency (over 757 ms) slow roundtrip
• Data within the US usually arrives at its
  destination within 110-120 ms
• Overseas transmissions require more time

7
What devices are part of an ISP?

• Network devices
• transmit and receive data from your computer
• E-mail servers
• handle incoming and outgoing mail for subscribers
  
• Web servers
• host subscriber Web sites
• Domain nameserver
• Looks up domain names

8
Why does the Internet use TCP/IP?

• Provides a standard
• TCP/IP is glue that holds the Internet together
• Easy to implement
• Public
• Internet is not owned or controlled by any single
  entity
• Free

9
What are IP Addresses?

• Defines the format for the addresses that
  identify computers on the Internet
• A series of numbers, example 204.127.129.001
• Separated into four sections by periods
• 8 bits per section x 4 sections 32 bits total
• Each sections number cannot exceed 255
• Static IP address
• Permanently assigned
• ISPs
• Dynamic IP address
• Temporarily assigned
• Clients
• IP addressing scheme provides approximately 4.3
  billion unique addresses

10
Whats a Domain Name?

• Hard to remember long strings of numbers
• Host computers have names called domain names
• Domain name
• fully qualified domain name (FQDN)
• usually typed in all lowercase
• key component of URLs and e-mail addresses
• highline.edu/tostrander
• tostrand_at_highline.edu
• Top-level Domains
• biz, com, edu, gov, info, int, mil, mil, org

11
How are domain names related to IP addresses?

• Each domain name corresponds to an IP address
• Domain name system
• Huge database that houses names and IP addresses
• Domain name servers
• Computers that house the database

12
How do dial-up connections work?

• Call is routed through the telephone companys
  local switch to the ISP

13
How does a modem work?

• Modem - modulate and demodulate
• Modulation changes signal from digital to
  analog
• Demodulation changes signal back from analog to
  digital
• Speed measured in megabits per second (e.g. 56
  Kpbs)

14
How does a cable modem work?

• Cabling system branches out from cable company
  (head-end)
• Signals are sent to individual homes
• Router and high-speed connection from the
  head-end to the Internet provides Internet
  connectivity

15
How secure is a cable modem connection?

• Always-on connection
• A hacker who discovers a security weakness can
  easily find it again
• High-speed access makes it a desirable target
• Use firewall software

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What are ISDN, T1, T3 and DSL?

• High-speed Internet access
• Digital communications links for voice and data
• ISDN
• Integrated Services Digital Network
• 64 Kbps or 128 Kbps
• All digital
• Able to carry voice and data
• Good option for businesses with small LANs

• T1
• High-speed 1.544 Mbps digital network
• Consists of 24 individual channels (64 Kbps for
  each)
• Popular for businesses and ISPs
• T3
• 672 channels
• Supports data rates of about 43 Mbps
• Sometimes referred to as DS3 (Digital Service-3)
  lines
• Provide many of the links on the Internet
  backbone

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What is DSL?

• Digital Subscriber Line
• High-speed, always-on, Internet access technology
  
• Runs over standard phone lines
• Several versions exist
• ADSL, SDSL, HDSL
• xDSL refers to entire group of DSL technologies

18
How does satellite access work?

• Direct satellite service (DSS)
• uses a satellite to send television, voice, or
  computer data directly to a satellite dish
• Two-way satellite service
• ships both upstream and downstream data through
  the satellite

19
Mobile Internet Access

• Can be used to surf the Web and check e-mail
• Wi-Fi hotspot
• wireless broadband Internet service offered in
  public locations
• WISPs maintain Wi-Fi hotspots
• WAP (Wireless Access Protocol)
• communications protocol that provides Internet
  access from handheld devices

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Whats the best Internet connection?