INFORMATION TECHNOLOGY IN BUSINESS AND SOCIETY SESSION 6 – HOW COMPUTERS AND THE WEB WORK SEAN J. TAYLOR

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

LEARNING OBJECTIVES 1.Understand basic computer architecture and how it has been enabled by layering platforms and Moore’s law. 2.Be able to explain how the Internet functions at a high level.

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

BASIC COMPUTER ARCHITECTURE: INFORMATION REPRESENTATION Numbers Text Pictures Audio 42  IT  gif,.jpeg,.bmp,… AU-Sun, WAV-MS, AIF-Apple, MP3

Understanding Binary:ASCII coding scheme

FROM ANALOG TO DIGITAL DATA

FROM ANALOG TO DIGITAL DATA

FROM ANALOG TO DIGITAL DATA

BASIC COMPUTER ARCHITECTURE

UBIQUITOUS COMPUTING

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

TELLING COMPUTERS WHAT TO DO

THE INTERNET

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

HOW IT BEGAN: THE INTERNET IN 1969 Interface Message Processors (IMPs) – packet switching nodes used to connect to ARPANET

ARPANET 1971

ARPANET 1980

SIMPLIFIED STRUCTURE OF THE INTERNET Hierarchy of privately-owned networks 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

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 Internet Backbone Carriers ISP

THE INTERNET

LAYERS

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.

PACKET-SWITCHED NETWORKS Data is sent as a sequence of ‘packets’ 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’ Packetize, transmit, reassemble. …… Packets ……… Message Network

PROTOCOLS AND TCP/IP Effective communication requires rules Protocol: A set of rules for transmitting data between computers Example: TCP/IP The ‘rules’ in a protocol answer questions like: 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? IP address 32-bit number given to each device connected to the Internet

OSI 7 LAYER MODEL Coaxial Cable, Twisted Pair Ethernet IP TCP HTTP SSL

INTERNET PROTOCOL 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., 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 leading seller of routers?

From: To: IPXpress Internet Delivery Envelope seanjtaylor.com TCP OVER IP IP and TCP protocols allow any two computers on the Internet to exchange data

TRANSMISSION CONTROL PROTOCOL

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?

HTTP: HYPERTEXT TRANSFER PROTOCOL

HTTP IN ACTION

“THE ELEMENTS OF COMPUTING SYSTEMS” “WEAVING THE WEB” (TIM BERNERS-LEE)

NEXT CLASS: COMPUTERS AND THE WEB II HTML tutorial