1. Data Communications 1

2. The Basic Communication Model
Sender
Coder
Channel
Decoder
Receiver 2

3. The Basic Communication Model
Send
Sender
Coder
Coder
Channel
Decoder
Receiver
The Basic Communication Model 3

4. Computer-based Data Communications
Data communications definition:
The movement of coded data and information from one point to another by means of electrical or electromagnetic devices, fiber-optical cables, or microwave signals. Also called teleprocessing, telecommunications, telecom, and datacom. 4

5. The Basic Data Communications Schematic
Terminal
Modem
Channel
Modem
Computer 5

6. Basic Data Communications Schematic
Terminal
to Modem
to Channel
to Computer
A modem is always required between a telephone and a digital computer. 6

7. Types of Networks (interconnected datacom devices)
WAN (wide area network)
Covers a large geographic area
Includes a wide variety of circuits
Usually includes host computers
LAN (local area network)
Limited area but could include 100 or so micros
Facilitates office automation
MAN (metropolitan area networks)
spans one city/metropolitan area 7

8. Communications Network
An Expanded Data
Communications Network
Visual display terminals
Multiplexer
Cluster
control
unit
Modem
Hard copy terminals
Other
types of
terminals
Channel
Multiplexer
Front-end
processor
Host
computer
Modem 8

9. Terminal Types Keyboard CRT - Cathode Ray Tube
VDT - Video Display Terminal
Hardcopy terminal
Teleprinter terminal 9

10. Terminal Types (continued)
Keyboard terminals
Push-button telephone
Point-of-Sale (POS)
Data collection
Special purpose 10

11. Other Data Communications Hardware
Cluster control unit -- controls multiple terminals in an area
Modem -- rated speed of bits per second determines transmission speed. Like a pipe determines water flow.
Multiplexer -- allows multiple terminals to share a single channel. 11

12. Channel WAN channel components Local loop IXC circuit (interexchange)
Typical circuitry
Twisted pair (4 wires)
Coax (buried)
IXC circuit (interexchange)
Microwave
Fiber-optical cable 12

13. The Channel of a Wide Area Network Earth Satellite Local Earth loop
User’s
modem
IXC circuit
Local
loop
Earth
station
(interexchange
channel)
Earth
station
Telephone
company
central office
Microwave
tower
IXC circuit
(interexchange
channel)
Microwave
tower
Local
loop
Telephone
company
central office
User’s
modem
Telephone
company
central office
Telephone
company
central office 13

14. Front-end Processor Ports Serial versus parallel transmission
Message switching, store and forward
Host 14

15. The Front-end Processor
Software
Channel
Interface Units
Host Computer
Interface
Parallel transmission
Serial
To host
transmission
Secondary storage 15

16. Data Communications Software
Host (telecommunications monitor or TCM)
Front-end processor (network control program) 16

17. Telecommunications Monitor (TCM)
Host
Prioritize
message 3 4
Security
log 1 2
Maintain
security log
Interface
with DBMS
DBMS
Primary
storage
status
Backup and
restart 17

18. Network Control Program (NCP)
Poll terminals such as roll call polling
Maintain a record of activity; date and time stamps
Convert codes
Editing such as error checking and reformatting
Add and delete routing codes
Maintain a history file of messages
Maintain statistics on network use

19. Data Communications Links the General Systems Model Elements
T = terminal
Standards
Information
processor T
Environment T
Management T
Input T
Transformation T
Output T

20. Basic Network Approaches
Timesharing
Distributed processing
Client/server computing
Clients are users, typically using workstations networked to form LANs
Server is a mainframe, mini, or even a micro 20

21. Basic Network Approaches (continued)
Complex software permits resource sharing
Combines central computing (MIS, DP) with end-user computing 21

22. A Timesharing Network
Legend:
Computer
Terminal 22

23. A Distributed Processing Network
Legend:
Central
Distributed
Computer
Computer 23

24. Common Carriers Services Integrated services digital network (ISDN)
Public-measured
Private (a.k.a. leased or dedicated line)
Integrated services digital network (ISDN) 24

25. ISDN- Integrated Services Digital Network
Simultaneous multimedia transmissions
Two types of channels
B channel carries data
D channel carries signals
Data
Signals 25

26. Two Standard Structures
Basic access (typically residential)
2 B 64 kbps ea.
1 D 16 kbps
Primary access (typically business)
23 B 64 kbps ea.
1 D 64 kbps 26

27. Local Area Networks File server, network server Peripherals Circuitry
Owned by using firm
Twisted pair is least expensive
Coax handles videoconferencing
Fiber-optics is most secure 27

28. LAN Software
Novell (NetWare) and Microsoft (Windows NT) are leading vendors of LAN software
Software allows servers and peer-to-peer connections

29. A Local Area Network Users Workstation 1 Manager 1 Letter Quality
Printer
Workstation 2
Network
Server
Secretary 1
Users
Workstation 3
Plotter
Secretary 2
Hard
Disk
Workstation 4
Manager 2
A Local Area Network 29

30. LAN Control Methodologies
Contention-based (Ethernet)
First-come, first-served
Collisions occur when load is heavy
Token-passing (IBMs Token Ring Network)
Token -- set of data bits required to send a message 30

31. Highlights in MIS Mobile computing Wireless networks cellular
wireless Lans
wide-area wireless
paging networks

32. A Network with Mobility Capability
MU MU MU
MU MU MU
Fixed host
MSS
MSS
Fixed
network
Fixed host
Fixed host
MSS
MSS
Fixed host
MU MU
MSS = mobile support station
MU = mobile units
MU MU MU MU

33. Network Management 1. Network planning 2. Network control
Capacity planning
Staff planning
Performance monitoring
2. Network control
3. Network manager
Staff
Network analysts (a type of systems analyst)
Software analysts (specialize in datacom software)
Datacom technicians (specialize in hardware)
LAN managers 33

34. The Intranet Intranet applications policy and procedure manuals
Product and pricing information
Employee information
Job openings
Documents needing signatures
Schedules and calendars
Access to databases
Access to groupware

35. The Intranet (continued)
Steps to a successful Intranet
1. Determine information needs
2. Establish Intranet policy
3. Build an Intranet staff
4. Provide for end user document preparation
5. Determine whether to outsource the Intranet service
6. Select the Intranet outsourcer
7. Provide datacom services
8. Build in Intranet security
9. Monitor system performance

36. Intranet Implementation Steps
Yes No
1. Determine
information needs
5. Outsource?
2. Establish
Intranet policy
6. Select the Intra-
net outsourcer
7. Provide datacom
resources
3. Build an
Intranet staff
8. Build in Intra-
net security
4. Provide for end user
document preparation
9. Monitor system
performance