Inside the Internet and the Web

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Chapter 10

• Inside the Internet and the Web

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Origins

• 1969 ARPANET (Advanced Research Projects Agency
  NETwork)
• Computer Scientists envisioned a need for
  efficient sharing of resources and ideas.
• Military strategists wanted a network that could
  function if some connections were destroyed.
• ARPANET was used by hundreds of military and
  university users until 1990.

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The Internet A Network of Networks

• The Internet is an interconnected network of
  thousands of networks linking academic, research,
  government, and commercial institutions.

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Internet Services

• The Internet provides scientists, engineers,
  educators, students, business people, and others
  with a variety of services such as
• Electronic mail (send/receive mail messages)
• Remote login (Telnet - access to other computers)
• Transferring files (FTP - accessing archives of
  data)
• Newsgroups (Usenet - on-line public discussions)
• World Wide Web (a collection of multimedia
  documents)

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Counting Connections

• Today, the Internet connects computers to about
  every country in the world. However, the
  Internet is
• growing too fast to measure its growth
• too decentralized to quantify
• a network with no hard boundaries
• One agency, www.internic.net, does perform some
  Management functions

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Internet Protocols

• The language at the heart of the Internet is
  TCP/IP
• Transmission Control Protocol/Internet Protocol
• Define how information can be transferred between
  machines and how machines on the network can be
  identified with unique addresses.

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Internet Protocols

• TCP breaks messages into packets
• Each packet has all the information needed to
  travel from network to network
• Host systems called Routers determine how to
  route transmissions

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Internet Protocols

• IP is the address for the packets
• Each Internet host computer has a unique IP
  Address
• Each address is comprised of four sets of numbers
  separated by periods, such as 123.23.168.22

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Internet Access Options

• Direct (dedicated) Connection
• (T1 or T3 lines)

• Computer has its own IP address and is attached
  to a LAN
• No need to dial up
• Files are stored on your computer
• Response time is quick

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Internet Access Options

• Dialup Connections
• limited connection using a modem
• slowest speeds
• Broadband Connections
• DSL (Digital Service Line) service is newer,
  faster, and cheaper than the older ISDN and
  allows sharing of telephone lines

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Internet Access Options

• Other types of Broadband Connections
• Cable Modem Connection
• allow Internet connections using shared TV cables
• Carry increased privacy and security risks
• Satellite Connections
• provides connections using DirecTV satellite
  dishes
• Wireless Broadband Wi-Fi
• Uses short-range radio waves

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Internet Access Options

• Internet Service Providers (ISPs)
• local ISPs provide connections through local
  telephone lines
• national ISPs offer connections on a nationwide
  scale

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Internet Addresses

• E-mail addresses are made upof two parts
  separated by an at(_at_) sign
• User name_at_host name
• Example johnsmith_at_mindspring.com
• The host is named using DNS (domain name system),
  which translates IP addresses into a string of
  names.

Each person on the Internet has a unique
e-mail address created by having a squirrel run
across a computer keyboard. Dave Barry
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Internet Addresses

• An Internet address includes username_at_hostname.su
  b.dom

• username is the persons mailbox
• hostname is the name of the host computer and is
  followed by one or more domains separated by
  periods
• host.subdomain.domain
• host.domain
• host.subdomain.subdomain.domain

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Internet Addresses

• Top level domains include

• .edu - educational sites
• .com - commercial sites
• .gov - government sites
• .mil - military sites
• .net - network administration sites
• .org - nonprofit organizations

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Internet Addresses
Examples
User President whose mail is stored on the host
whitehouse in the government domain

• president_at_whitehouse.gov

User hazel_filbert at the server for Lane County,
Oregon, k-12 school district
hazel_filbert_at_lane.k12.or.us
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Inside the World Wide Web

• WWW is a distributed browsing and searching
  system developed at CERN
• System was designed to give Internet documents
  unique addresses
• HTML language was created for encoding and
  displaying documents
• Browser software was built for viewing documents
  from remote locations

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Browsing the Web
Web site Jargon

• Web pages are made up of text and images
• A Web site is a collection of web pages
• A Home page is the main entry to a Web site
• A Web browser like Netscape Communicator or
  Internet Explorer allows you to explore the Web
  by clicking links

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Browsing the Web
Hyperlinks (links) are words or pictures that
act as buttons, allowing you to go to another Web
page

• Links are typically underlined or displayed in a
  different color

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More on Browsing the Web

• More Web site Jargon
• Links allow you to locate information without
  knowing its exact location (it may move from time
  to time)
• Back and Forward buttons let you retrace your
  steps
• Bookmarks and Favorites can be set up to mark
  your favorite Web locations

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Web Addresses
A typical URL (Uniform Resource Locator) looks
like this http//www.prenhall.com.beekman
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Web Addresses

• Dissecting Web Page address

• Protocol for Web pages

Resource Page
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Searching the Web

• Search engines
• produce a list of pages that match a keyword
• they are built around a database that catalogs
  Web locations based on content
• Directory or Subject Tree
• A hierarchical catalog of Web sites
• Natural Language
• Ask questions

The ability to ask the right question is more
than half the battle of finding the
answer. Thomas J. Watson
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Search Engines

• Search engines help find information when you
  type a query using keywords.

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Search Engines

• Directory/subject tree engines offer a
  menu of subject choices

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Search Engines

• Ask questions in a Natural Language Search
  Engine

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Portals

• Portals offer quick and easy access to a
  variety of services such as e-mail,
  chat,maps, news, shopping, etc.
• Examples of consumer portals include
• Yahoo!, Excite, Lycos, Alta Vista, Netscape
  Netcenter, Snap
• Specialized portals target specific industries
  and economic sectors

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