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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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The Internet

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The internet l.jpg

The Internet


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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 (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


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Networks – Benefits

  • Benefits of networks

    • Convenience

    • Resource sharing

    • Facilitates communication

    • Saves money

    • Reliability

    • Scalability


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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


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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)


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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


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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)


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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


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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


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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


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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


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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


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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


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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


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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)


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IP Address (con’t)

  • Static IP address

    • Permanent

    • Connection through router

  • Dynamic IP address

    • Changes with each Internet connection

    • Connection through ISP


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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


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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


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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


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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


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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


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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


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Internet Culture

  • Critical Evaluation of Information

  • Freedom of Expression

  • Communication Mechanisms

  • Advertising

  • Societal Impact


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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


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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


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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 $)


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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


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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


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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


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