1. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
Chapter 6
Data Communications
© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke

2. This Could Happen to You
Dee needs to decide where she will run the blog
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
Protected by firewall
Employees access through VPN
Can be protected from unauthorized access
Sales people can access with same password they already use

3. Study Questions 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?

4. What Is a Computer Network?
Collection of computers
Communicate with one another over transmission line
Three basic types
Local area network (LAN)
Wide area network (WAN)
Internet

5. LAN Connects computers residing in single location
2 to several hundred computers
One geographic area
Communication lines can be placed where the organization wants

6. WAN Connect computers in different geographical areas
Two or more cities
Uses communication networks from vendors
Licensed by government

7. Internet Network of networks Connect LANs, WANs, and other internets
Private networks of networks
Use a variety of communication methods and conventions
Seamless flow of data provided by layered protocol
Set of rules that communicating devices follow

8. What Are the Components of a LAN?
Local area network
Computers connected on single company site
Usually located within half mile area
Property controlled by company operating network
Company can run cabling as necessary
Components
Switch
Special purpose computer that receives and transmits messages
Network interface card (NIC)
Hardware that connects each device’s circuitry to the cable
Onboard NIC or card that fits into an expansion slot

9. NIC Devices MAC address Media connections Unique identifier
Unshielded twisted pair (UTP) cable
RJ-45 connector
Optical fiber cables
Light rays reflected inside glass core surrounded by cladding
Uses ST and SC connectors

10. IEEE 802.3 Protocol Ethernet protocol standard
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

11. LANs with Wireless Connections
Wireless NIC (WNIC)
LAN operation
NICs operate on protocol
WNICs operate on protocol
WNICS connect to access point (AP)
AP processes both standards

12. What Are the Alternatives for a WAN?
WANs connect computers at separate sites
No cabling between sites
Cable connections made through licensed communications companies
Internet service provider (ISP)
Provides legitimate Internet address
Serves as gateway to Internet
Pay for Internet

13. Connecting to the ISP Connections made through:
Regular telephone lines
Use of DSL line
Cable TV lines
All require digital data to be converted to analog
Modem makes conversion

14. MIS In Use: Larry Jones (Student) Network Services
Larry set up LAN networks
Realized that he had to offer support
Customers had problems
Customers needed to add more devices
Coupled installation with support package
Extra charges for support beyond normal wear and tear

15. Dial-Up Modems 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

16. DSL Modems 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
Asymmetric digital subscriber lines (ADSL)
Symmetrical digital subscriber lines (SDSL)

17. Cable Modems Provide high-speed data transmission
Use cable television lines
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
Performance varies based on number connected

18. Cable Modems, continued
Download speed up to 10Mbps, upload up to 256 kbps
Operate with Layer 1 and 2 protocols
Speeds
Narrowband
Transmission speeds less then 56 kbps
Broadband
Transmission speeds in excess of 256 kbps

19. Networks of Leased Lines
WAN connects computers located at geographically distributed sites
Access devices connect sites to transmission
Switch
Router
Alternative is leasing lines
T1, T3
Set up as a point-to-point line
Only predefined sites can use leased lines
Provide low cost per bit transmitted

20. Transmission Line Types, Uses, and Speeds
Figure 6-11

21. Problem Solving Guide: Thinking Exponentially Is Not Possible, but…
Nathan Myhrvoid claimed that:
Humans cannot think exponentially
Think of fastest linear change and extrapolate from there
Was writing about growth of magnetic storage
Also applies to growth of computer network phenomena
Ubiquitous and cheap connectivity is growing exponentially
What are the threats and opportunities?

22. Exponential Phenomena Brings Changes
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
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

23. Public Switched Data Network (PSDN)
Network of computers and leased lines
Developed and maintained by vendor
Time leased on network
Utility that supplies network for other companies to lease
Each site leases line to connect to PSDN network at access point
Point of presence (POP)
Saves setup and maintenance activities

24. PSDN Protocols Frame relay Asynchronous transfer mode (ATM) Ethernet
Process traffic at 56 kbps to 40 Mbps
Simplest and easiest to support
Asynchronous transfer mode (ATM)
Process speeds from 1 to 156 Mbps
Ethernet
Operates at speeds of 10 to 40 Gpbs

25. Criteria for Comparing WANs
Costs
Setup costs
Examples: costs of acquiring lines and equipment
Operational costs
Examples: lease fees, ISP charges, training
Maintenance costs
Examples: periodic maintenance, repair, upgrades

26. Criteria for Comparing WANs, continued
Performance
Speed
Latency
Availability
Loss rate
Transparency
Performance guarantees
Growth potential
Length of contract commitment

27. Security Guide: How Does Encryption Work?
Process of transforming clear text into coded text
Used for secure storage or communication
Uses algorithms
DES, 3DES, AES
Key
Used to encrypt data
Algorithm applies key to produce coded message
Symmetric encryption
Asymmetric encryption

28. Security Guide: How Does Encryption Work?, continued
Public key/private key
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
Secure communication over Internet
Encrypted using SSL/TLS protocol
Encodes messages using Web site’s public key, decoded with private key

29. What Is the Purpose of a Firewall?
Computer device that prevents unauthorized network access
May be special-purpose computer or program
Organizations may have multiple firewalls
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

30. What Is a VPN and Why Are VPNs Important?
Virtual private network
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
Private pathway over shared network
Secure, encrypted communications

31. Ethics Guide: Human Networks Matter More
Six degrees of separation
Often unaware of those in the chain
Build personal human networks for success
Someone, somewhere that you need to know or will need to know
Meet people at professional and social situations
Pass out and collect cards
Converse to expand network
Look for new channels
Social network theory
Weak and strong ties

32. How Does the Knowledge in This Chapter Help Dee?
Dee and salespeople use thin client computers
Dee creates blog entries on Web pages using Moveable Type
Salespeople use pages served by Moveable Type
Client computers contain VPN client software
Interacts with VPN server via Internet
Secure, private connections
Firewalls stop traffic not addressed to VPN server
Salespeople know how to use VPN

33. How Does the Knowledge in This Chapter Help Dee?, continued
IT department cannot schedule resources to setup blog server in timely fashion
Will not allow outside person to do setup
Would then have access to system
Consultant can create server on unprotected test server
Can be copied onto network server after acceptance
Requires some internal IT labor
Consultant could include Trojan horse virus or malware
Install only software from known sources
Code should not reside on production server

34. How Does the Knowledge in This Chapter Help Dee?, continued
Dee negotiates with IT department
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

35. Active Review 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?