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Week 4

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British political cartoon, Punch magazine, 1851. What ... hub at the center of this network is a very simple piece of ... known as a LAN (local area network) ... – PowerPoint PPT presentation

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Title: Week 4


1
Week 4
  • A summary of previous 3 weeks

2
Cartoon
"New Siamese Twins" The telegraph links England
and France British political cartoon, Punch
magazine, 1851
3
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.

It has following parts
  • 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

4
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.

5
The System Unit
What are common components inside the system unit?
6
Central Processing Unit
  • What 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

7
Central Processing Unit
  • What are the components of the central
    processing unit (CPU )?

8
Central Processing Unit
  • What is the control unit?
  • A component of the CPU that directs and
    coordinates most of the operations in the
    computer

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

9
Central Processing Unit
  • What is the arithmetic/logic unit (ALU)?

p. 4.6
10
Central Processing Unit
  • What is the arithmetic/logic unit (ALU)?

p. 4.6
11
Central Processing Unit
  • What is a machine cycle?
  • Together the four operations of the CPU comprise
    a machine cycle

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 4 The results of the math problem are
stored in memory The result in memory displays
on the screen of the monitor
Step 3 The ALU executes the math problem
12
Data Representation
  • What is a byte?
  • 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

13
Memory
  • How much RAM is needed?
  • The more RAM, the more programs and files a
    computer can work on at once

p. 4.18 Fig. 4-22
14
Ports
  • What is a port?
  • 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

Click to view Web Link then click Ports and
Connectors
p. 4.25 Fig. 4-32
15
Ports
  • What is a serial port?
  • 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
16
Ports
  • What is a parallel port?
  • 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
17
Week2
18
Electronic Commerce (2002)
SOME TECHNOLOGIES USED
SOME INFORMATION GATHERED
SEARCH ENGINE
SEARCH BEHAVIOR
BUYER LOCATES SELLER
ON-LINE CATALOG
BROWSING BEHAVIOR
RECOMMENDER AGENT
CUSTOMER PREFERENCES
CONFIGURATOR
SELECTION OF GOODS
EFFECTIVENESS OF PROMOTIONS
SHOPPING BOT
BARGAINING STRATEGIES
AGGREGATOR
PRICE SENSITIVITIES
INTERNET
NEGOTIATION
AUTOMATED AGENTS
PERSONAL DATA
TRANSACTION PROCESSOR
SALE
MARKET BASKET
DATA INTERCHANGE
CREDIT/PAYMENT INFORMATION
PAYMENT
CRYPTOGRAPHY
DELIVERY REQUIREMENTS
E-PAYMENT SYSTEMS
DELIVERY
TRACKING AGENT
ON-LINE PROBLEM REPORTS
ON-LINE HELP
POST-SALE ACTIVITY
CUSTOMER SATISFACTION
INFORMATION
BROWSER SHARING
FOLLOW-ON SALES OPPORTUNITIES
PHYSICAL
INTERNET TELEPHONY
19
eCommerce Technology
  • Infrastructure Electronic payments
  • Wireless technologies Content delivery
  • Search engines Intelligent agents
  • Access security Data mining
  • Data interchange Mass personalization
  • Security

20
E-Commerce Infrastructure
  • What worldwide structure is required to support
    e-Commerce?
  • Network
  • Machines
  • Protocols
  • Security
  • Payment

21
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

22
Routing
Machine 2.16
Machine 1.35 wants to send a packet to Machine
3.249. Routers determine the path the packet
will take.
Machine 3.249
B
A
Machine 1.35
Router A can send the packet either way
4.1
5.9
NETWORK 4 ITS ROUTER
NUMBER OF ROUTES
ROUTING STATISTICS
23
Web Server Basics
24
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.

25
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.
26
Server Workflow
27
Web Architecture
How are web sites constructed?
TIER 1
TIER 2 Server
TIER 3 Applications
TIER 4 Database
SOURCE INTERSHOP
28
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.

29
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.

30
A Wide Area Network
When an organizations LAN are connected together
over a larger geographical region, perhaps the
world, they are called Wide area network. A
router sends or route packets from one LAN to
another LAN
31
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.

32
  • Most packets are split into three parts

33
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)

34
Payload -
  • Also called the body or data of a packet. This is
    the actual data that the packet is delivering to
    the destination.

35
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.

36
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

37
  • 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

38
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.

39
  • Specifically the IP address has the following
    form
  • NetworkHost
  • 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.

40
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.
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