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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.

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Presentation on theme: "The Internet. Networks - Overview Internet – a network of networks Overview of networks A network consists of two or more computers connected together."— Presentation transcript:

1 The Internet

2 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

3 Networks – Overview (cont) 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

4 Networks – Benefits Benefits of networks Convenience Resource sharing Facilitates communication Saves money Reliability Scalability

5 Internet Growth 433+ million computers linked as of 01/2007 (http://www.isc.org/index.pl)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

6 Internet Protocols Protocols – rules that describe how computers communicate; some common protocols: FTP (File Transfer Protocol) protocols – SMTP, POP, IMAP HTTP (HyperText Transfer Protocol) TCP/IP (Transmission Control Protocol/Internet Protocol)

7 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

8 TCP/IP (cont) Example 1: Sending an message Formatted according to Simple Mail Transfer Protocol (SMTP) Example 2: Requesting a Web page Formatted according to Hyper Text Transfer Protocol (HTTP)

9 TCP/IP (cont) 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

10 TCP/IP (cont) 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

11 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

12 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

13 Types of Internet Connections (cont) 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 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

14 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

15 IP Address Unique numerical name identifying each computer on Internet vs. Domain Name People-oriented unique name using symbols; e.g., 32 bits (four bytes) – 1 byte can represent the numbers 0 thru 255 Four natural numbers separated by dots (i.e., ) Network component and host component

16 IP Address (cont) Vital in packet switching Internet Assigned Numbers Authority (IANA) Operating unit of Internet Corporation for Assigned Names and Numbers (ICANN) – 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)

17 IP Address (cont) Static IP address Permanent Connection through router Dynamic IP address Changes with each Internet connection Connection through ISP

18 IP Address (cont) 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 2 32 addresses; IPv6 supports addresses Simplified IP headers Reduction of header fields in IP packet Added security features

19 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 ) (4) Browser establishes TCP connection to above (5) Browser sends a request for what portion

20 Web Page Retrieval (cont) Enter a URL (cont) (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

21 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

22 World Wide Wait (cont) 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

23 Issues and Predictions Intranets Isolated, private network with an internal Web Cost Inexpensive – time to charge more? Internet2 - 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

24 Internet Culture Critical Evaluation of Information Freedom of Expression Communication Mechanisms Advertising Societal Impact

25 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

26 Communication Mechanisms and mailing lists Internet Relay Chat (IRC) Instant Messaging (AOLs IM and ICQ) Blogs Newsgroups Videoconferencing Emoticons and shorthand Flaming and SHOUTING

27 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 $)

28 On-line Businesses Types: Advertising, marketing, partnership, retail, service, software, subscription On-line business hurdles: Privacy and security Cookies - File (on your disk) containing data about you Created while on-line Filling out a form/registering Encrypted Setting a cookie Persistent cookie

29 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

30 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 Intelligent form Version control Videoconferencing


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