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Information technology in business and society

Information technology in business and society. Session 6 – How Computers and the Web work Sean J. taylor. Administrativia. Facebook Experiment: See Beibei Li in 8-186 Friday 2pm-4pm to receive payment Varun’s office hours on Monday: 2-4pm in 8 th floor tutoring area Assignment 1

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Information technology in business and society

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  1. Information technology in business and society Session 6 – How Computers and the Web work Sean J. taylor

  2. Administrativia • Facebook Experiment: See Beibei Li in 8-186 Friday 2pm-4pm to receive payment • Varun’s office hours on Monday: 2-4pm in 8th floor tutoring area • Assignment 1 • My office hours: moved to 3:30-5:30pm on FRIDAY (temporarily)

  3. Learning objectives • Understand basic computer architecture and how it has been enabled by layering platforms and Moore’s law. • Be able to explain how the Internet functions at a high level.

  4. Why we care? “We’re in an engineering culture. You couldn’t put a [Rupert] Murdoch or a [Michael] Eisner in charge of a company [like Google]. It’s been tried. Terry Semel led Yahoo. I just spent some time with Google engineers. I couldn’t understand a thing they were saying. I don’t think [Semel] understood the engineers’ language, so he couldn’t challenge them. I suspect that’s one reason he didn’t last” Ken Auletta, SIIA keynote, 1/30/2008

  5. Basic computer architecture:Information representation • Numbers • Text • Pictures • Audio 42  00101010 IT 01001010 01010100 .gif, .jpeg, .bmp,… AU-Sun, WAV-MS, AIF-Apple, MP3

  6. Understanding Binary:ASCII coding scheme

  7. FROM ANALOG TO DIGITAL DATA 000000000000 000111111000 001100001100 001000000100 010010010010 010000000010 010000000010 001011110100 001100001100 000111111000 000000000011 000000000011

  8. FROM ANALOG TO DIGITAL DATA 000000000000 000111111000 001100001100 001000000100 010010010010 010000000010 010000000010 001011110100 001100001100 000111111000 000000000011 000000000011 000000000000 000111111000 001100001100 001000000100 010010010010 010000000010 010000000010 001011110100 001100001100 000111111000 000000000011 000000000011

  9. Basic Computer Architecture

  10. Ubiquitous computing

  11. Computer Basics: Hardware • Central processing unit (CPU): the actual hardware that interprets and executes software instructions and coordinates how all the other hardware devices work together. • Intel: 286386486Pentium I,II,III,IV, AMD Athlon, IBM PowerPC, Sun SPARC, MIPS • Random Access Memory (RAM): The place to keep the data and applications while the computer is running • Storage: A tool you use to store information for use at a later time • floppy disks, CD, DVD, Hard Disks, tape

  12. Telling Computers what to do

  13. The internet

  14. WHAT IS THE INTERNET? • A very large network of computers that “speak” IP (and usually TCP as well) • All connected to each other (hence a “network”) • Information exchanged between two computers may pass through several other computers

  15. How it began: The Internet in 1969 Interface Message Processors (IMPs) – packet switching nodes used to connect to ARPANET

  16. Arpanet 1971

  17. Arpanet 1980

  18. Hierarchy of privately-owned networks Simplified structure of the Internet • Backbone network: High speed, city-to-city, with network access points, owned by large service providers (AT&T, Sprint, Level3) • ISP networks: Connect from backbone to local areas (typically providing access to consumers) • Local access networks: Access to individual computers • Internet: • No single authority • No single control source • No single entry point • No single type of application

  19. Internet Backbone Internet backbone • Set of interconnected Wide Area Networks (WANs) • Similar to the Interstate Highway network • WAN owners (backbone providers) compete with each other • Several connections converge at a Network Access Point (NAP). Each NAP has at least one intelligent device – transitional data communication facilities. • Backbone providers own and maintain devices at NAPs ISP ISP Carriers

  20. The Internet

  21. The Internet

  22. Layers

  23. Why is Internet Structure Strategic? • Resilient. One node goes down, others don’t. • Intelligence is at the edges. • Content agnostic. • Application agnostic. • No single authority controls it. • Extensible – Can always add more.

  24. 01101010101000010101011100 Data is sent as a sequence of ‘packets’ Packetize, transmit, reassemble. • Packet Switched vs. Circuit Switched Networks • It isn’t cost effective to have telephone-like connections between different communicating computers • This is primarily because data transmission is ‘bursty’ 01101010101000010101011100 01101010101000010101011100 Packets …….. 0110110111101111101111101010110111……….01110 Message Packet-switched networks Network

  25. Protocols and TCP/IP Effective communication requires rules The ‘rules’ in a protocol answer questions like: IP address • Protocol: A set of rules for transmitting data between computers • Example: TCP/IP • How do I write down the address of the computer I want to send my packet to? • Where do I send the next packet I get? • How do I detect the beginning of a new packet? • How do I figure out an error in transmission? • 32-bit number given to each device connected to the Internet

  26. Ethernet IP TCP HTTP SSL Coaxial Cable, Twisted Pair OSI 7 Layer Model

  27. Internet Protocol 127.18.47.145 127.47.17.47 • Each Internet computer (host) has an IP address • String of 32 ones and zeros (IPv4 -> IPv6) • Usually represented by four number segments separated by dots: dotted decimal notation, e.g., 128.171.17.13 • IP names (e.g., www2.nyu.edu) correspond to IP addresses • Routers • Connect the Internet’s individual networks (subnets) • Cooperate to give an end-to-end route for each packet • Need to be very fast • Who is the world’s leadingseller of routers?

  28. From: 128.122.199.131 To: IPXpressInternet Delivery Envelope 216.115.102.78 TCP over IP seanjtaylor.com • IP and TCP protocols allow any two computers on the Internet to exchange data www.yahoo.com

  29. Transmission Control Protocol

  30. DNS: Understanding Domains • DNS is the Internet’s “directory assistance” linking IP names to IP addresses • A computer’s IP name tells you a lot; e.g., the type of organization supporting the Web site • Top-level domain: the last part of IP names, e.g., • com – commercial or for-profit business • edu – educational institution • gov – U.S. government agency • mil – U.S. military organization • net – Internet administrative organization • org – professional or non-profit organization • biz – business • pro – accountants, doctors, and lawyers, to start • How do you get a domain name?

  31. HTTP: Hypertext transfer protocol

  32. HTTP In action

  33. “The elements of computing systems” “Weaving the Web” (Tim Berners-Lee)

  34. Next Class:Computers and the Web II • HTML tutorial

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