Week 4

A summary of previous 3 weeks

Cartoon

"New Siamese Twins"The telegraph links England and FranceBritish political cartoon, Punch magazine, 1851

What are Fiber Optics

• Fiber optics (optical fibers) are long, thin strands of very pure glass about the diameter of a human hair. They are arranged in bundles called optical cables and used to transmit light signals over

long distances.

•core - thin glass center of the fiber where the light travels •cladding - outer optical material surrounding the core that reflects the light back into the core •buffer coating - plastic coating that protects the fiber from damage and moisture

It has following parts:

How Does an Optical Fiber Transmit Light?

• Suppose you want to shine a flashlight beam down a long, straight hallway.

• Just point the beam straight down the hallway -- light travels in straight lines, so it is no problem.

• What if the hallway has a bend in it? You could place a mirror at the bend to reflect the light beam around the corner. What if the hallway was very winding with multiple bends? You might line the walls with mirrors and angle the beam so that it bounces from side-to-side all along the hallway. This is exactly what happens in an optical fiber.

Processor Memory module

Processor Memory module Expansion cards

• Sound card• Modem card• Video card• Network

interface card

Ports and Connectors

Processor Memory module Expansion cards

• Sound card

Processor Memory module Expansion cards

• Sound card• Modem card

Processor Memory module Expansion cards

• Sound card• Modem card• Video card

Processor Memory module Expansion cards

• Sound card• Modem card• Video card• Network

interface card

Processor

The System UnitThe System UnitWhat are common components inside the system unit?

Central Processing UnitCentral Processing UnitWhat is the central processing unit (CPU)?

Interprets and carries out the basic instructions that operate a computer

Most devices communicate with the CPU in order to carry out a task Also called the processor

Central Processing UnitCentral Processing UnitWhat are the components of the central processing unit (CPU )?

CPU

Arithmetic/Logic Unit

(ALU)

Control Unit

CPU

Arithmetic/Logic Unit

(ALU)

Central Processing UnitCentral Processing UnitWhat is the control unit?

Control UnitControl Unit

The control unit repeats a set of four basic operations:

Fetch – obtain a program instruction or data item from memory

Decode - translate the instruction into commands

Execute - carry out the command Store - write the result to memory

A component of the CPU that directs and coordinates most of the operations in the computer

CPU

Control Unit

What is the arithmetic/logic unit (ALU)?Central Processing UnitCentral Processing Unit

.and.

.and.

.not.

.not..or..or.

Component of the CPU Performs arithmetic, comparison, and logical

operations Performs the execution part of the machine cycle

Arithmetic/Logic Unit

(ALU)

p. 4.6

Next

Arithmetic (addition, subtraction,

multiplication, and division)

What is the arithmetic/logic unit (ALU)?Central Processing UnitCentral Processing Unit

Comparison (greater than, equal

to, or less than)

.and.

.and.

.not.

.not..or..or.Logical

(AND, OR, NOT)

p. 4.6

Central Processing UnitCentral Processing Unit

A student enters a math problem into the memory of the computer

Step 1: The control unit fetches the math problem from memory

Step 2: The control unit decodes the math problem and sends it to the ALU

Step 3: The ALU executes the math problem

Step 4: The results of the math problem are stored in memory

The result in memory displays on the screen of the monitor

What is a machine cycle?Together the four operations of the CPU comprise a

machine cycle

Data RepresentationData RepresentationWhat is a byte?

8-bit byte for the number 3

8-bit byte for the number 5

8-bit byte for the capital letter T

Eight bits are grouped together to form a byte 0s and 1s in each byte are used to represent

individual characters such as letters of the alphabet, numbers, and punctuation

Software package usually indicates how much RAM is required

MemoryMemory

The more RAM, the more programs and files a computer can work on at once

How much RAM is needed?

p. 4.18 Fig. 4-22

Next

PortsPortsWhat is a port?

Click to view WebLink then click Ports and Connectors

keyboard

USBUSB

mouse

telephone line in

game port

monitor

svideo out

network

printer (parallel port)

cable TV

speaker

serial port

microphone

telephone line out

FM reception

Used to connect external devices to the system unit

Port is the interface, or point of attachment, to the system unit

Most located on the back of the system unit

p. 4.25 Fig. 4-32

Next

PortsPortsWhat is a serial port?

serial transmission of data

DB-9 female connector

byte representation for number 3 (00110011) byte

representation for number 5 (00110101)

DB-9 male connector

byte representation for number 1 (00110001)

Transmits one bit of data at a time

Used to connect devices that do not require fast transmission rates• mouse• keyboard• modem

Two common types• 25-pin• 9-pin

p. 4.27 Fig. 4-35

Next

PortsPortsWhat is a parallel port?

byte representation for number 1byte representation for number 3byte representation for number 5

DB-25 male connector

DB-25 female connector

Connects devices that can transfer more than one bit at a time

Usually used for printers Two newer types

• EPP (Enhanced Parallel Port)

• ECP (Extended Capabilities Port)

IEEE 1284 is a standard that specifies how older and newer peripheral devices transfer data to and from a computer

p. 4.27 Fig. 4-36

Next

Week2

Electronic Commerce (2002)

BUYERLOCATESSELLER

NEGOTIATION

PAYMENT

SALE

DELIVERY

POST-SALEACTIVITY

SELECTIONOF GOODS

SEARCH ENGINE

SHOPPING BOT

AGGREGATOR

ON-LINE CATALOG

AUTOMATED AGENTS

TRACKING AGENT

ON-LINE HELP

INTERNET TELEPHONY

CUSTOMER PREFERENCES

BARGAINING STRATEGIES

PRICE SENSITIVITIES

CREDIT/PAYMENT INFORMATION

ON-LINE PROBLEM REPORTS

FOLLOW-ON SALES OPPORTUNITIES

SOME TECHNOLOGIES USED: SOME INFORMATION GATHERED:

BROWSING BEHAVIOR

DELIVERY REQUIREMENTSE-PAYMENT SYSTEMS

CONFIGURATOR

RECOMMENDER AGENT

TRANSACTION PROCESSOR

DATA INTERCHANGE

CRYPTOGRAPHY

BROWSER SHARING

MARKET BASKET

PERSONAL DATA

CUSTOMER SATISFACTION

SEARCH BEHAVIOR

EFFECTIVENESS OF PROMOTIONS

INFORMATION

PHYSICAL

eCommerce Technology

• Infrastructure • Electronic payments• Wireless technologies • Content delivery• Search engines • Intelligent agents• Access security • Data mining• Data interchange • Mass personalization

• Security

E-Commerce Infrastructure• What worldwide structure is required to support e-

Commerce?• Network• Machines• Protocols• Security• Payment

Client/Server Architecture• Fundamental Internet structure• Client requests service; server provides it• Data exchanged only through real-time messages• Server may become a client to a different server

Server 2respondsto client 1

The Internet

Client 1 requestsservice from server 21

2

3

Client 2 requestsservice from server 3

Server 3 respondsto client 2

Routing

Router A can sendthe packet either way

Machine 1.35 wants to send apacket to Machine 3.249.

Routers determine the paththe packet will take.

Routers

A BMachine1.35

Machine3.249

NETWORK 4 & IT’S ROUTER

Machine2.16

4.1

5.9

ROUTING STATISTICSNUMBER OF ROUTES

Web Server Basics

Internet Server

• The server is the heart of the technical architecture, receiving requests from Internet users, retrieving the information locally or from networked devices and replying.

• Selection and sizing of this machine is critical task, typically presenting a tradeoff between performance and cost.

Web Server Web server - A Web server is a piece of computer software that can respond to a browser's request for a page, and deliver the page to the Web browser through the Internet.

You can think of a Web server as an apartment complex, with each apartment housing someone's Web page.

In order to store your page in the complex, you need to pay rent on the space. Pages that live in this complex can be displayed to and viewed by anyone all over the world.

Your landlord is called your host, and your rent is usually called your hosting charge.

Every day, there are millions of Web servers delivering pages to the browsers of tens of millions of people through the network we call the Internet.

Server Workflow

Web Architecture

SOURCE: INTERSHOP

How are web sites constructed?

TIER 1TIER 2Server

TIER 3Applications

TIER 4Database

Communication

• Communication is often defined as the exchange of information between two individuals using a common set of symbols, signs or behavior.

• More specifically, telecommunications usually involves a significant distance between the individuals and some electronic equipment for transmission and reception of the information.

• Data communications really is nothing more than the transmission of ones and zeros from one point to another.

Computer Network Basics

• This is called a star network. • The hub at the center of this network is a very simple piece of networking hardware that takes the

data from one computer and passes them onto the other computers in the network• This is also known as a LAN (local area network). A LAN is a communications network consisting

of cables, computers and network devices confined to a very small geographic region such as a building or floor of a building.

Hub

Desktop PC Workstation

Laptop

Server

Laser Printer

A Wide Area Network

Hub

Desktop PC Workstation

Laptop

Server Laser Printer

Router Router Hub

Desktop PC Workstation

Laptop

Server

Laser Printer

Copper wireFiber

Wireless

Chicago San Antonio

When an organization’s LAN are connected together over a largergeographical region, perhaps the world, they are called Wide area network.A router sends or route packets from one LAN to another LAN

Packet Switching

• An Alternative to circuit switching is packet switching.

• When sending a message over a network (e.g. an email) the message is usually broken up into a smaller set of messages called packets.

• Most packets are split into three parts:

Header

• The header contains instructions about the data carried by the packet. These instructions may include:

• Length of packet (some networks have fixed-length packets, while others rely on the header to contain this information)

• Packet number (which packet this is in a sequence of packets) • Protocol ( the protocol defines what type of packet is being

transmitted: e-mail, Web page, streaming video) • Destination address (where the packet is going) • Originating address (where the packet came from)

Payload -

• Also called the body or data of a packet. This is the actual data that the packet is delivering to the destination.

Trailer

• The trailer, sometimes called the footer, typically contains a couple of bits that tell the receiving device that it has reached the end of the packet. It may also have some type of error checking.

Packet Example

• As an example, let's look at how an e-mail message might get broken into packets. Let's say that you send an e-mail to a friend.

• The e-mail is about 3,500 bits (3.5 kilobits) in size. The network you send it over uses fixed-length packets of 1,024 bits (1 kilobit). – The header of each packet is 96 bits long and the trailer is 32 bits

long, leaving 896 bits for the payload.

• To break the 3,500 bits of message into packets, you will need four packets (divide 3,500 by 896). Three packets will contain 896 bits of payload and the fourth will have 812 bits. Here is what one of the four packets would contain:

• Each packet's header will contain the proper protocols, the originating address (the IP address of your computer), the destination address (the IP address of the computer where you are sending the e-mail) and the packet number (1, 2, 3 or 4 since there are 4 packets). Routers in the network will look at the destination address in the header and compare it to their lookup table to find out where to send the packet. Once the packet arrives at its destination, your friend's computer will strip the header and trailer off each packet and reassemble the e-mail based on the numbered sequence of the packets

IP Numbers

• All IP addresses have the same format. – Four sets of numbers separated by three

periods.

• Each of the four sets of numbers requires one byte (8 bits) for a total of 32 bits.

• By convention we are stating the IP address in decimal rather than binary format.

• Specifically the IP address has the following form – Network:Host – For example in the IP address 128.135.130.201

• The network address is 128.135. – This is the address that all computers in University of Chicago

share

• IP address maybe subdivided into a subnetwork and machine number. – In the host number 130.201 the 130 denotes a particular

LAN (Stuart Hall) and 201 is the machine number in that LAN.

Domain Name System

• Domain names must get converted or resolved into IP addresses.

• This is done through an Internet Service called the domain name system.

• This system makes use of special servers called domain name servers.