Transcript Volume 1 2.9

Volume 1
Volume 1 2.9
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Definition of Computer Networking

Computer networking concerns with a
collection of computers and peripherals
that are interconnected through wireless
technology.
Tom, Thank you
I’ve got it.
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Computer Networking
Below items can be shared by different
users in the network:
(a) Hardware devices
(b) Software application
(c) Data
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A. Local Area Networks (LANs)
1. Definition of a LAN

a network of a personal computer or
workstation that spans a relatively small
physical area
2. Advantages of Using LANs

can transmit large amounts of data

can transmit data at very fast rate
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3. Disadvantages of Using LANs

The connection distance and the number of
computers attached to a single LAN are
limited.
4. Different Types of Topologies in a LAN
Bus Topology
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Ring Topology
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Star Topology
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5. Transfer Protocols

the message transfer is managed by a
transfer protocol such as the TCP/IP
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TCP/IP enables the Internet to detect and
correct transmission problems automatically
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TCP/IP connection is primarily point-to-point
6. Controlling Software

the network operating system, such as
NetWare, Unix, Linux or Microsoft Windows,
that resides in the server
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7. Access Methods
the physical transfer of data is performed by
an access method such as the Ethernet or
Token Ring
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8. Communications Paths

the telephone lines, coaxial cables, optical
fibers and so on that connect the network
adapters
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B. Wide Area Networks (WANs)

a network of LANs that spans a relatively
large geographical area
A comparison of a LAN and a WAN
LAN
WAN
Definition
Network of personal computers
or workstations that spans a
relatively small physical area.
Network of LANs that
spans a relatively large
geographical area.
Covered
Area
A single building or group of
buildings.
A city, a country or
even the world.
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A. Wire-based Communications Channels
1. Telephone Lines

communications channels that can be found
all over the world
Pairs of insulated
copper wires
Telephone line
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Twisted-pair wire
A Twisted-pair cable
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
In order to connect to the
Internet through telephone
lines, we have to use
modems.
Internal and External Modems
Internal Modem
Appearance
Position
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Expansion board
Inserted into vacant
expansion slots.
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External Modem
Expansion board
Attached to computers
through the standard
RS-232.
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2. Coaxial Cables


used for cable television and computer
network connections
more expensive than
telephone lines, but can
transmit much more
data at a time
Insulating material
Woven or braided metal
Plastic outer coating
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Central wire
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3. Optical Fibers

used extensively by telephone
companies to rebuild their
communications infrastructure
Data transmitted within an optical fiber
Signals
Transmitted as light rays
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Several fibers are bundled into a common
sheath to form a fiber cable
Optical Fiber
Fiber Cable
Optical
Fibers
Transparent
core
Layers of
moisture barrier
sheathing and
impact-resistant
plastic jackets
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Light-reflecting
cladding layers
Opaque plastic
protective coating
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Advantages of using optical fibers over
telephone lines or coaxial cables
(1) greater bandwidths  the transmission
speed is faster
(2) data can be transmitted digitally
(3) not susceptible to electrical interference
(4) much more difficult to tamper with
(5) much thinner and lighter
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Disadvantages of using optical fibers
over telephone lines or coaxial cables
(1) more expensive to install
(2) more easily damaged
(3) more difficult to split
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B. Wireless Communications Channels
1. Analogue and Digital Signals from
Land-based Antennas
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used for cable television broadcast, interurban telephone traffic and so on
Signals carried
by microwave
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Microwave
antenna
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Advantages of using land-based
microwave antennas over
telephone lines or coaxial cables
(1) no need to install any cables
(2) installation and maintenance costs of
cables can be saved
(3) communications mobility is higher
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2. Analogue and Digital Signals from
Communications Satellites
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used for global positioning, navigation
and messaging services
in a circular orbit above
the earth
more expensive than
land-based microwave
antennas
can view a stationary patch which covers
more than one-third of the global
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3. Infrared Waves from Infrared Devices
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used for short-distance remote controls
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transmission and reception by invisible band
of radiation
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4. Radio Waves from Bluetooth Devices
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

used
for
short-distance
communications
mobile
speed is up to 720Kbps
data transfer within a
range of 10 metres
use omnidirectional radio
waves that can transmit
through non-metal barriers
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State
two
kinds
of
wireless
communication channels and compare
their differences based on the following
criteria:
(a) way
(b) speed
(c) limitations
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Back
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