1. Laudon & Laudon: Canadian Edition
Chapter 7
Telecommunications – Part 1
In the continuing saga towards our greater understanding of management information systems, we will now discuss the concepts of telecommunications and networks.
The importance of these topics cannot be overestimated since without telecommunications networks, communicating over long distances and sharing electronic information would not be possible.
The ability to do both of these things is vital for and information society.

2. Information Systems for Management
Outline
Telecommunications Model
Analog Signal
Digital Signal
Communication media (twisted wire, coaxial cable, fibreoptic, microwave, satellite signalling)
Computer Network
Local Area Network (LAN)
Wide Area Network (WAN)
Network Hardware
Network Software
Network Topology
Packet and Circuit Switching
Telecommunications
Information Systems for Management

3. Information Systems for Management
Telecommunications
sender
receiver
relay
electronic signal (message)
channel
Telecommunications: Electronic data transfer (communications) over some a channel (medium).
Telecommunications system contains:
Sender & Receiver
Message - Data that is transmitted as a signal over a channel
Channel - The medium by which data or voice are transmitted
between sender and receiver (e.g., twisted wire, optical cable, air—
microwave, satellite signaling)
Other equipment (switch, relay, modem, gateway, etc.)
Telecommunications
Information Systems for Management

4. Types of Signals Analog signal Continuous waveform
Can get all the ranges
Use: voice communications
Example: electrical light
Digital signal
Discrete waveform
Two states: 0 and 1 (On-off electrical pulses)
Use: data communications
Example: computer, computer nets
Modem (MOdulation / DEModulation)
Converts digital into analog, and analog into digital signals
Telecommunications
Information Systems for Management

5. Telecomm Media & Transmission Speeds
Total amount of data transmitted through a telecommunications channel measured as bits per second.
Medium
Speed
Fiber optic cable
6 Tbps
Coaxial cable
1Gbps
Twisted wire
Up to 1Gbps
Microwave
600 Mbps
Satellite
bps=bits per second; Kbps=kilobits (103); Mbps=megabits (106); Gbps=gigabits (109); Tbps=terabits (1012)
Telecommunications
Information Systems for Management

6. Information Systems for Management
Networks
Network - A set of nodes (computers, printers, and other equipment) and linking media.
Types of networks based on:
Topology (configurations of nodes and links; e.g., star network)
Geographic scope – LAN vs. WAN
Communications method – Circuit vs. Packet
Telecommunications
Information Systems for Management

7. Information Systems for Management
Star Network
All computers are connected to a central node (e.g. hub, computer, switch, controller).
All communications between computers must pass through the central node.
Better communications control, but the central node is critical (high-risk).
hub, switch, controller, or computer
Telecommunications
Information Systems for Management

8. Information Systems for Management
Bus Network
All computers are linked by a single circuit
All messages are broadcast to the entire network
Simple communications management as signals can travel both directions as needed, but collision possible.
Telecommunications
Information Systems for Management

9. Information Systems for Management
Ring Network
All computers are linked by a closed loop
Data is passed in one direction from one node to another
Better control and no collision, but communications management more complex than with bus.
Telecommunications
Information Systems for Management

10. Laudon & Laudon: Canadian Edition
LAN vs. WAN
Local Area Network (LAN)
Network covering a smaller area (one or more buildings like campus)
Wide Area Network (WAN)
Network covering a larger area (a region, world)
Examples: IBM’s SNET, Internet
Many student labs will have Lans, shared printers, etc.
Telecommunications
Information Systems for Management

11. Information Systems for Management
Circuit Switching
Circuit Switching
Entire message travels from switch to switch
Used for analog signals
(classical telephone network)
Source: TechWeb
Telecommunications
Information Systems for Management

12. Information Systems for Management
Packet Switching
Packet Switching
Sender breaks message into small packets
Packets are routed in the most economical way by different routes
Receiver reassembles the message
Internet works this way
Telecommunications
Information Systems for Management

13. Information Systems for Management
Network Hardware
Router, Switch –most used today
Devices for managing communications on a network
Telecommunications
Information Systems for Management

14. Information Systems for Management
Network Software
Network Operating System (NOS)
Software that routes and manages communications & resources (e.g., Ethernet OS for bus network, IBM toke Passing Ring OS for ring network, Windows Server and Client NOS)
Network Protocol
Rules that govern communications between network nodes (e.g., how computers on a bus network communicate;
TCP/IP – how computers on different networks communicate)
NOS can support a certain protocol and more than one (TCP/IP today supported by most NOSes)
Telecommunications
Information Systems for Management

15. Transfer Control Protocol & Internet Protocol (TCP/IP)
Defines the Internet – how different networks (NOSes, hardware, application and system software) communicate with each other.
Four layers:
(SMTP),
file transfer (FTP,
HTTP
TCP IP
Telecommunications
Information Systems for Management

16. Information Systems for Management
How Internet Works
SENDER
RECEIVER
SMTP to TCP:
“Take this message
and send it to this
address”.
TCP Breaks message into
packets and passes
to IP.
IP Looks up Internet
addresses and
routers on the way to
receiver. Puts address
on each packet and
passes to Network.
Puts packets on com-
munication medium.
SMTP restores original format
of message and presents it.
TCP Put packets back to the
Whole in proper orders and
Checks sum of data received
vs. sum sent.
IP Accepts packets and
reports back to routers.
Gets packets off com-
munication medium.
See: How SMTP and TCP/IP work
Telecommunications
Information Systems for Management