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The Internet Networks - Overview Internet – a network of networks Overview of networks A network consists of two or more computers connected together Common components include: Client computers Server computers Shared devices Cables, hubs, and routers that provide the network connections

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networks overview
Networks - Overview
  • Internet – a network of networks
  • Overview of networks
    • A network consists of two or more computers connected together
    • Common components include:
      • Client computers
      • Server computers
      • Shared devices
      • Cables, hubs, and routers that provide the network connections
networks overview con t
Networks – Overview (con’t)
  • One way to describe networks is by their size:
    • LAN (Local Area Network) – single building, relatively short distance
    • WAN (Wide Area Network) – spans a large geographic area; Internet can be considered a large WAN
    • Also:
      • MAN (Metropolitan Area Network) – spans a distance larger than a LAN but smaller than a WAN
      • WLAN (Wireless Local Area Network) – uses WiFi wireless network technology
      • PAN (Personal Area Network) – organized around an individual; can involve cell phone, PDA, mobile computer, etc.
      • CAN (Campus Area Network) – spans multiple LANs but smaller than a MAN; used on a college campus
networks benefits
Networks – Benefits
  • Benefits of networks
    • Convenience
    • Resource sharing
    • Facilitates communication
    • Saves money
    • Reliability
    • Scalability
internet growth
Internet Growth
  • 433+ million computers linked as of 01/2007 (http://www.isc.org/index.pl)
  • Reasons for success:
    • Decisions not politically based
    • Internet is distributed operation
    • Homogeneity of language and outlook
    • Inherently interested people
    • Free (or inexpensive) software
internet protocols
Internet Protocols
  • Protocols – rules that describe how computers communicate; some common protocols:
    • FTP (File Transfer Protocol)
    • Email protocols – SMTP, POP, IMAP
    • HTTP (HyperText Transfer Protocol)
    • TCP/IP (Transmission Control Protocol/Internet Protocol)
tcp ip
TCP/IP
  • TCP/IP (Transmission Control Protocol/Internet Protocol):
    • How computers connect, send, and receive information
    • TCP permits communication between computers
    • IP specifies how data is routed to and from computers
    • TCP and IP are primary protocols but TCP/IP refers to a whole suite of protocols
    • Called “language of the Internet”
    • Mandated in 1983 for all ARPANET hosts
tcp ip con t
TCP/IP (con’t)
  • Example 1: Sending an e-mail message
    • Formatted according to Simple Mail Transfer Protocol (SMTP)
  • Example 2: Requesting a Web page
    • Formatted according to Hyper Text Transfer Protocol (HTTP)
tcp ip con t9
TCP/IP (con’t)
  • TCP is responsible for splitting the message into IP packets; each packet contains:
    • Piece of message
    • Information about sender
    • Information about receiver
    • Sequence number
    • Error checking information
tcp ip con t10
TCP/IP (con’t)
  • IP is responsible for routing the packets to the correct destination address
  • At destination (receiving) computer TCP is responsible for:
    • Reassembling message
    • Sending requests for corrupt packets to be resent
  • Advantages of packets:
    • Error recovery
    • Load distribution
    • Flexibility
physical components
Physical Components
  • Servers
    • Answer service requests
  • Routers
    • Direct data packets
  • Networks
    • Transport packets
    • Copper wires, fiber-optic cables, radio waves, microwaves, infrared light, and visible light
types of internet connections
Types of Internet Connections
  • Analog – regular dial-up - up to 56 Kbps
  • ISDN (Integrated Services Digital Network) –up to 128 Kbps
  • Broadband connections – faster than analog and ISDN:
    • xDSL (Digital Subscriber Line) – permanent connection that uses phone line but does not tie up your connection; 128 Kbps to 8 Mbps
    • Cable – permanent connection that operates over cable TV lines; 512 Kbps to 20 Mbps
types of internet connections con t
Types of Internet Connections (con’t)
  • Other types of connections:
    • Wireless Internet connections – uses radio frequency bands instead of telephone or cable networks (newer technology)
    • T-1 lines – leased line option; used by businesses connecting to Internet and by ISPs connecting to the Internet backbone. Dedicated phone connection that supports data rates of 1.544 Mbps
    • T-3 lines – used to connect to backbone and for the backbone itself. 43 to 45 Mbps
    • IoS – Internet over Satellite; access via satellite
isps nsps
ISPs, NSPs
  • Internet Service Provider (ISP)
  • Network Service Provider (NSP)
    • Local ISPs can connect to NSPs
    • Leased-lines from local telephone companies provide part of the network
    • Transmit data at 1.54 megabits (Mbps)
  • Backbone Provider – organization that supplies access to high-speed transmission lines used to connect to the Internet; some providers include: MCI, Sprint, UUNET, AGIS, BBN
ip address
IP Address
  • Unique numerical name identifying each computer on Internet
  • vs. Domain Name
    • People-oriented unique name using symbols; e.g., www.amazon.com
  • 32 bits (four bytes) – 1 byte can represent the numbers 0 thru 255
    • Four natural numbers separated by dots (i.e., 72.21.203.1)
    • Network component and host component
ip address con t
IP Address (con’t)
  • Vital in packet switching
  • Internet Assigned Numbers Authority (IANA)
    • Operating unit of Internet Corporation for Assigned Names and Numbers (ICANN) – http://www.icann.org/index.html
    • Assigns and manages IP addresses
  • IP address to domain names
    • Resolver converts symbolic name to IP address
  • Programs convert IP addresses to symbolic names (vice versa)
    • nslookup (UNIX-based systems)
ip address con t17
IP Address (con’t)
  • Static IP address
    • Permanent
    • Connection through router
  • Dynamic IP address
    • Changes with each Internet connection
    • Connection through ISP
ip address con t18
IP Address (con’t)
  • IPv6 or IPng - latest version of Internet Protocol (IP or IPv4)
  • Major changes:
    • More addresses
      • IP address size from 32 bits to 128 bits
      • IPv4 supports 232 addresses; IPv6 supports 2128 addresses
    • Simplified IP headers
      • Reduction of header fields in IP packet
    • Added security features
web page retrieval
Web Page Retrieval

Enter a URL (how://where/what)

(1)Browser determines URL using “how” part

(2)Browser queries the DNS for IP address using “where” part

(3)DNS responds with IP address (e.g. - 172.132.173.2)

(4) Browser establishes TCP connection to above

(5) Browser sends a request for “what” portion

web page retrieval con t
Web Page Retrieval (con’t)

Enter a URL (con’t)

(6) Server services request by sending back the “what” part

(7) TCP connection closed

(8) Browser renders text portion of HTML

(9) Browser repeats steps for in-line image files

(10)Browser displays images as retrieved

world wide wait
World Wide Wait
  • Congestion issues and delays caused frustration
  • Resulted from popularity
  • Reasons:
    • Increase in Internet users - why?
    • Elaborate Web pages contain images, sounds, video clips
world wide wait con t
World Wide Wait (con’t)
  • World Wide Web Consortium (W3C) issues:
    • “Save the Internet from the Web”
    • Improving process of connecting
    • New techniques to expedite Web page requests
    • Refining how URL resolved
  • Web page design suggestions:
    • Avoid unnecessary graphics
    • Cascading Style Sheets (CSS)
    • PNG instead of GIF
issues and predictions
Issues and Predictions
  • Intranets
    • Isolated, private network with an internal Web
  • Cost
    • Inexpensive – time to charge more?
  • Internet2 - http://www.internet2.edu
    • Networking consortium that facilitates the development, deployment and use of revolutionary Internet technologies.
    • For schools, libraries, universities, researchers
    • Much higher speeds – Abilene network backbone supports transfer rates 100 to 1000 times faster than typical broadband connections
internet culture
Internet Culture
  • Critical Evaluation of Information
  • Freedom of Expression
  • Communication Mechanisms
  • Advertising
  • Societal Impact
freedom of expression
Freedom of Expression
  • Lack of regulation
  • Blue ribbon graphic
  • Obscene or offensive material
  • Censorship
  • Platform for Internet Content Selection (PICS)
    • Set of technical specifications for designating labels
    • Works with vendor-supplied filtering software
communication mechanisms
Communication Mechanisms
  • E-mail and mailing lists
  • Internet Relay Chat (IRC)
  • Instant Messaging (AOL’s IM and ICQ)
  • Blogs
  • Newsgroups
  • Videoconferencing
  • Emoticons and shorthand
  • Flaming and SHOUTING
societal impact
Societal Impact
  • Advertising
    • Clickable images
    • Revolving advertisements
    • Spam
  • Internet related jobs
  • Information and communication
    • Weather, news, stock prices, travel information
  • How we shop / bank / invest (spend $)
on line businesses
On-line Businesses
  • Types: Advertising, marketing, partnership, retail, service, software, subscription
  • On-line business hurdles:
    • Privacy and security
    • Cookies - http://www.cookiecentral.com
      • File (on your disk) containing data about you
      • Created while on-line
        • Filling out a form/registering
        • Encrypted
      • Setting a cookie
      • Persistent cookie
business and safety security
Business and Safety/Security
  • Secure payment (credit cards); Secure Electronic Transactions (SET); Electronic money
  • Legal Environment
    • New and uncharted territory
    • Taxes and tariffs
  • President Clinton (July 1997) - Framework for the Global Electronic Commerce
      • Policy on Global Information Infrastructure (GII)
      • Principles:
        • Encourage self-regulation of Internet
        • Should not restrict e-commerce
        • Provide legal environment
        • Acknowledge uniqueness
        • Promote globally
collaborative computing
Collaborative Computing
  • Applications that allow sharing of information and resources between people
    • World Wide Web
      • Collaborative computing platform supporting HTML
    • Groupware
      • Collaborative computing platform software on networked computer system
    • E-mail
    • Intelligent form
    • Version control
    • Videoconferencing