BU115: Computer Concepts Lecture Slides

1
BU115 Computer ConceptsLecture Slides
Communications Technology
2
Review HTML

• Introduction
• What is a web page?
• What is HTML?
• Anatomy of a web page
• How to develop a web page
• How to display/publish a web page

3
Review HTML
Common Tag Groups Basic required for page
structure Text affect the text appearance
e.g. headings, bold, etc Links provide
hypertext links to other pages, users
Formatting affect the page layout e.g. breaks,
lists Graphical introduces images, lines
Tables to create tables for organizing text
4
Communications Technology

• Bus 115

5
Course Map
Communications
Describe Properties
Comm Media
Internet
Networks
Comm Devices
Define Services Benefits Topologies
Describe Services Protocols
Comm Software
Purpose Function
6
Communications Technology
Learning Objectives

• 1. Basic principles and terminology of
  communications
• 2. The major communications media and
• 3. Characteristics of data transmission
• 4. Communications devices/processors
• 5. Networks defined, purpose and benefits
• 6. The major network topologies.

7
The Information System
1
2
3
4
5
6. Communications
8
Definitions
Communications Concepts

• Tele/Communications - the (electronic) transfer
  of signals over distance. (voltage/radio/light)
• Connectivity - the ability of computers (and IT
  devices) to send and receive signals among one
  another.

9
Definitions
Communications Concepts

• Types of Signals
• Analogue - wave-form continuous.
• Digital - discrete on/off.

• MOdulation - converting digital to analogue
• DEModulation - analogue to digital.

10
Digital vs. Analog
11
Modem Communications
Digital Transmission
Digital Transmission

HI!
HI!
Analog Transmission
MOdulate - DEModulate
12
Modems

• Type Internal vs External
• Speed (Baud rate)
• 14.4, 28.8, 33.6, 56 Kbps, MBs
• Standards Hayes, USR/3Com, V.90/Flex
• ADSL (phone line) Bell HSE
• Cable/wireless modems (Rogers, Look)
• Asynchronous Digital Subscriber Line

13
Role of Communications Software
Communications Concepts

• Protocols /Handshaking
• Error Correction
• Data Compression
• Remote Control
• Terminal Emulation

14
Communications Media

• Media channels/cables along which signals are
  sent.
• Media Characteristics
• Frequency - cycles per sec (MHz)
• Wavelength - short (micro)/long
• Amplitude height of wave
• Bandwidth - range of frequency
• Baud (Rate) - speed (bits per sec)

15
Communications Media

• Twisted-Pair Cable
• Coaxial Cable
• Fiber-Optic Cable

Physical

• Microwave Systems (Terrestrial/Satellite)
• Wireless Systems (Radio/Infrared)

EM
16
Communications Media - Comparisons
17
Transmission Characteristics

• Line Configurations
• Ways of connecting devices
• Point-to-Point
• Multipoint

18
Transmission Characteristics

• Point-to-Point
• Each device connected by its own line

Devices
Host
19
Transmission Characteristics

• Multipoint
• All devices connected by sharing a single line

Devices
Host
20
Transmission Characteristics
Serial or Parallel Transmission
21
Transmission Characteristics

• Serial Data Transmission
• Bits are sent in series on a single line

Bits
22
Transmission Characteristics

• Parallel Data Transmission
• Bits are sent in 8 parallel lines (1 byte)

Byte
.
23
Transmission Characteristics

• Direction of Transmission Flow
• Simplex - one direction only

• Half-Duplex - two directions, but only one at a
  time

• Full-Duplex - both directions at the same time
  

24
Transmission Characteristics

• Transmission Mode
• Asynchronous vs Synchronous

25
Direction
26
Direction
Direction
27
Direction
Direction
28
Transmission Characteristics

• Transmission Mode
• Asynchronous - one byte at a time (start/stop
  bits, idle gaps)
• Synchronous - continuous stream with start/stop
  synch bytes

29
Transmission Characteristics

• Parity Bit
• Extra bit added to each byte
• For error detection (count of 1s)
• Even Parity - even number of 1s
• OR
• Odd Parity - odd number of 1s

30
Transmission Characteristics

• Parity Bit
• Even Parity - 1s add up to an even number
• OR
• Odd Parity - 1s add up to an odd number

31
Error Checking - The Parity Bit
EVEN Parity
32
Break Time
10 mins.
33
Transmission Characteristics

• Packet Switching (Internet)
• Data is sent as fixed-length packages of fixed
  size (e.g. 576 bytes)
• each packet includes address, etc. and makes its
  own way on the network.
• Multiplexing
• - Combining a number of low speed channels onto
  one high speed channel.

34
Packet SwitchingCommunication on the Net
Source
Web Servers
P1
P2
P3
P4
P1
P3
P2
P4
Target
35
Communications Processors

• Devices that assist in the communications
  process.

36
Communications Processors
Devices that assist in the communications
process.

• Multiplexers
• Concentrators
• Front-End Processors

37
Communications Processors
Multiplexing
38
Communications Processors
Workstations
Multiplexer I
Multiplexing
High Speed Line
Multiplexer II
Low Speed Lines
Mainframe
39
Network Linking Devices
Hubs - connect computers in a LAN Routers -
use IP address to route packets more
efficiently on the Internet Switches - high
speed traffic handling and IP
resolution Bridges - connect similar
networks Gateways - connect dissimilar networks
40
NETWORKS
QUESTIONS?

• What is a network?
• Why do organizations use networks?

41
NETWORK

• Definition
• A system of interconnected computer
  communications devices designed to permit the
  sharing of resources among many users.

42
Why Network?

• To share hardware resources
• To share software resources
• To share data and information
• To share expertise
• To exchange messages
• To collaborate on projects

43
Types of Networks

• Wide Area Network (WAN)
• National or Global
• Metropolitan Area Network (MAN)
• City or Metropolitan area
• Local Area Network (LAN)
• Building or campus

44
Networks

• Local Area Network (LAN)
• Components of a LAN
• Computers and peripherals (disks, printers)
• Cabling (communications media)
• Communications hardware (hub, switch)
• Communications software (Network Operating
  System)
• Network Interface Cards (NICs)

45
Networks

• Local Area Network (LAN)
• Types of LANs
• Peer-to-Peer - each PC at same level
• Client-server - one main PC (server) controls
  clients and resources
• Access Methods
• Polling - each device is checked
• Contention - first-come-first-served
• Token Passing - token holder has access to the
  line

46
Networks

• LAN Network Topologies

• Star
• Ring
• Bus

47
Star Topology
48
Bus Topology
49
Ring Topology
50
Hybrid Topology - Mix
51
Review Communications Technology
Questions Answers
52
Review Communications Technology Questions
Answers
1. Define and distinguish between a) modem b)
multiplexer. Both modems and multiplexers are
used in transmitting data signals along
communications lines. a) a modem is used to
convert signals from digital to analogue (and
back), when transmitting from computers via phone
lines. b) a multiplexer is used to combine the
signals from a number of low-speed lines on to
one high-speed line and separate them at the
destination.
53
Review Communications Technology Questions
Answers
2. Define, and state the purpose of a LAN.
Identify its major components. A LAN (Local
Area Network) is a set of interconnected computer
resources, within a limited geographic area
(building/campus). It is used to efficiently
share IT resources among users. The major
components include Computers and peripherals
(disks, printers) Cabling (communications
media) Communications hardware (hub,
multiplexer) Communications software (Network
Operating System) Network Interface Cards
54
Review Communications Technology Questions
Answers
3. What are five uses/benefits of
networks? Five benefits of networks are the
ability to 1. Share hardware resources 2. Share
software resources 3. Share data and information
4. Share expertise 5. Exchange messages
55
Communications Technology
QUIZ 7A/B
Next Class CH. 7 Uses of Communications
Technology