Transcript Ch06

Chapter 6
Data Communications
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
This Could Happen to You
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Dee needs to decide where she will run the blog
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It needs to be private to maintain a competitive advantage
Sales people need to have easy access
Passwords may be needed to restrict access
Emerson has a private network
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Protected by firewall
Employees access through VPN
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Can be protected from unauthorized access
Sales people can access with same password they already
use
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Study Questions
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What is a computer network?
What are the components of a LAN?
What are the alternatives for a WAN?
How does encryption work?
What is the purpose of a firewall?
What is a VPN and why is it important?
How does the knowledge in this chapter help
Dee?
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
What Is a Computer Network?
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Network
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Three basic types
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Collection of computers
Communicate with one another over transmission
line
Local area network (LAN)
Wide area network (WAN)
Internet
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
LAN
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Connects computers residing in single
location
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2 to several hundred computers
One geographic area
Communication lines can be placed where the
organization wants
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
WAN
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Connect computers in different geographical
areas
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Uses communication networks from vendors
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Two or more cities
Licensed by government
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Internet
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Network of networks
Connect LANs, WANs, and other internets
Private networks of networks
Use a variety of communication methods and
conventions
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Seamless flow of data provided by layered
protocol
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Set of rules that communicating devices follow
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
What Are the Components of a LAN?
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Local area network
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Computers connected on single company site
Usually located within half mile area
Property controlled by company operating network
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Components
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Switch
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Special purpose computer that receives and transmits
messages
Network interface card (NIC)
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Company can run cabling as necessary
Hardware that connects each device’s circuitry to the cable
Onboard NIC or card that fits into an expansion slot
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
NIC Devices
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MAC address
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Unique identifier
Media connections
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Unshielded twisted pair (UTP) cable
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Optical fiber cables
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RJ-45 connector
Light rays reflected inside glass core surrounded by
cladding
Uses ST and SC connectors
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
IEEE 802.3 Protocol
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Ethernet protocol standard
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Specifies hardware characteristics
Describes how messages are packages
Determines how messages are processed
Operates at Layers 1 and 2 of TCP/IP-OSI
architecture
Personal computers usually support 10/100/1000
Ethernet
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
LANs with Wireless Connections
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Wireless NIC (WNIC)
LAN operation
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NICs operate on 802.3 protocol
WNICs operate on 802.11 protocol
WNICS connect to access point (AP)
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AP processes both standards
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
What Are the Alternatives for a WAN?
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WANs connect computers at separate sites
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Internet service provider (ISP)
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No cabling between sites
Cable connections made through licensed
communications companies
Provides legitimate Internet address
Serves as gateway to Internet
Pay for Internet
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Connecting to the ISP
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Connections made through:
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All require digital data to be converted to
analog
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Regular telephone lines
Use of DSL line
Cable TV lines
Modem makes conversion
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
MIS In Use: Larry Jones (Student)
Network Services
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Larry set up LAN networks
Realized that he had to offer support
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Coupled installation with support package
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Customers had problems
Customers needed to add more devices
Extra charges for support beyond normal wear
and tear
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Dial-Up Modems
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Handles conversion between analog and
digital
Connection made by dialing ISP
Maximum transmission speed of 56kbps
Modulation governed by V.34, V.90. or V.92
standards
PPP controls message packaging and
handling
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
DSL Modems
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Operates over telephone lines
Do not interfere with voice telephone service
Faster data transmission than dial-up
Connection always maintained
Use their own Layer 1 and 2 protocols
Download and upload speeds vary
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Asymmetric digital subscriber lines (ADSL)
Symmetrical digital subscriber lines (SDSL)
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Cable Modems
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Provide high-speed data transmission
Use cable television lines
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High-capacity optical fiber cable run to
neighborhood distribution center
Television cables connect at distribution center
and runs to subscribers
Does not interfere with television transmission
Up to 500 subscribers connected at each center
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Performance varies based on number connected
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Cable Modems, continued
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Download speed up to 10Mbps, upload up to
256 kbps
Operate with Layer 1 and 2 protocols
Speeds
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Narrowband
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Broadband
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Transmission speeds less then 56 kbps
Transmission speeds in excess of 256 kbps
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Networks of Leased Lines
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WAN connects computers located at geographically
distributed sites
Access devices connect sites to transmission
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Alternative is leasing lines
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Switch
Router
T1, T3
Set up as a point-to-point line
Only predefined sites can use leased lines
Provide low cost per bit transmitted
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Transmission Line Types, Uses,
and Speeds
Figure 6-11
6-20
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Problem Solving Guide: Thinking
Exponentially Is Not Possible, but…
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Nathan Myhrvoid claimed that:
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Was writing about growth of magnetic storage
Also applies to growth of computer network
phenomena
Ubiquitous and cheap connectivity is growing
exponentially
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Humans cannot think exponentially
Think of fastest linear change and extrapolate from there
What are the threats and opportunities?
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Exponential Phenomena Brings
Changes
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Technology doesn’t drive people to do new things
Social progress occurs in small, evolutionary,
adaptive steps
Technology may enable a capability, but people may
not want it
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People want to do what they are doing more easily
They want to solve existing problems
Respond by hedging your bets
The more time involved, the more potential for error
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Public Switched Data Network
(PSDN)
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Network of computers and leased lines
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Developed and maintained by vendor
Time leased on network
Utility that supplies network for other
companies to lease
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Each site leases line to connect to PSDN network
at access point
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Point of presence (POP)
Saves setup and maintenance activities
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
PSDN Protocols
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Frame relay
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Asynchronous transfer mode (ATM)
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Process speeds from 1 to 156 Mbps
Ethernet
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Process traffic at 56 kbps to 40 Mbps
Simplest and easiest to support
Operates at speeds of 10 to 40 Gpbs
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Criteria for Comparing WANs
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Costs
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Setup costs
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Operational costs
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Examples: lease fees, ISP charges, training
Maintenance costs
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Examples: costs of acquiring lines and equipment
Examples: periodic maintenance, repair, upgrades
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Criteria for Comparing WANs,
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Performance
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Speed
Latency
Availability
Loss rate
Transparency
Performance guarantees
Growth potential
Length of contract commitment
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Security Guide: How Does
Encryption Work?
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Encryption
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Process of transforming clear text into coded text
Used for secure storage or communication
Uses algorithms
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Key
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Used to encrypt data
Algorithm applies key to produce coded message
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DES, 3DES, AES
Symmetric encryption
Asymmetric encryption
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Security Guide: How Does
Encryption Work?, continued
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Public key/private key
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Public key used to encrypt messages
Public key sent to other party to encode messages to be
sent back
Decoded with private key
Complex and slow
HTTPS
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Secure communication over Internet
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Encrypted using SSL/TLS protocol
Encodes messages using Web site’s public key, decoded with
private key
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
What Is the Purpose of a Firewall?
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Computer device that prevents unauthorized network
access
May be special-purpose computer or program
Organizations may have multiple firewalls
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Perimeter firewalls sit outside organizational network
Internal firewalls are inside network
Packet-filtering firewalls examine source address,
destination address, and other data before allowing
message to pass
May filter both incoming and outgoing messages
Access control list (ACL) encodes rules stating what
packets are allowed or prohibited
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
What Is a VPN and Why Are VPNs
Important?
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Virtual private network
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Uses Internet or private network to create
appearance of point-to-point connections
Uses public Internet to create appearance of
private network
Client and server have point-to-point connection
called tunnel
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Private pathway over shared network
Secure, encrypted communications
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Ethics Guide: Human Networks
Matter More
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Six degrees of separation
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Often unaware of those in the chain
Build personal human networks for success
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Someone, somewhere that you need to know or will need to
know
Meet people at professional and social situations
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Social network theory
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Pass out and collect cards
Converse to expand network
Look for new channels
Weak and strong ties
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
How Does the Knowledge in This
Chapter Help Dee?
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Dee and salespeople use thin client computers
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Client computers contain VPN client software
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Dee creates blog entries on Web pages using Moveable
Type
Salespeople use pages served by Moveable Type
Interacts with VPN server via Internet
Secure, private connections
Firewalls stop traffic not addressed to VPN server
Salespeople know how to use VPN
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
How Does the Knowledge in This
Chapter Help Dee?, continued
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IT department cannot schedule resources to setup
blog server in timely fashion
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Will not allow outside person to do setup
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Consultant can create server on unprotected test
server
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Can be copied onto network server after acceptance
Requires some internal IT labor
Consultant could include Trojan horse virus or malware
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Would then have access to system
Install only software from known sources
Code should not reside on production server
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
How Does the Knowledge in This
Chapter Help Dee?, continued
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Dee negotiates with IT department
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Threatens to set up own system of user Ids and
passwords
Says she will set up blog on public server
Would cause confusion that would add to IT
department’s work
Her proposal is the lesser of two evils
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Active Review
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6-35
What is a computer network?
What are the components of a LAN?
What are the alternatives for a WAN?
How does encryption work?
What is the purpose of a firewall?
What is a VPN and why is it important?
How does the knowledge in this chapter help
Dee?
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke