excellence publication co. ltd. volume 1 2.91 volume 1

Excellence Publication Co. Ltd.Volume 1 2.9 1

Volume 1Volume 1


Computer networking concerns with a collection of computers and peripherals that are interconnected through wireless technology.

Definition of Computer NetworkingDefinition of Computer Networking

Tom, Thank youTom, Thank youI’ve got it.I’ve got it.


(a) Hardware devices(a) Hardware devices

Computer NetworkingComputer Networking

(c) Data(c) Data

(b) Software application(b) Software application

Below items can be shared by different Below items can be shared by different users in the network:users in the network:


A. Local Area Networks (LANs)A. Local Area Networks (LANs)

1. Definition of a LAN1. Definition of a LAN a network of a personal computer or

workstation that spans a relatively small physical area

2. Advantages of Using LANs2. Advantages of Using LANs

can transmit large amounts of data

can transmit data at very fast rate


3. Disadvantages of Using LANs3. 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 LAN4. Different Types of Topologies in a LAN

Bus TopologyBus Topology Ring TopologyRing Topology Star TopologyStar Topology


5. Transfer Protocols5. Transfer Protocols

the message transfer is managed by a transfer protocol such as the TCP/IP

TCP/IP enables the Internet to detect and correct transmission problems automatically

TCP/IP connection is primarily point-to-point

6. Controlling Software6. Controlling Software the network operating system, such as

NetWare, Unix, Linux or Microsoft Windows, that resides in the server


7. Access Methods7. Access Methods

the physical transfer of data is performed by an access method such as the Ethernet or Token Ring

8. Communications Paths8. Communications Paths

the telephone lines, coaxial cables, optical fibers and so on that connect the network adapters


B. Wide Area Networks (WANs)B. Wide Area Networks (WANs)

a network of LANs that spans a relatively large geographical area

LANLAN WANWAN

Network of personal computers Network of personal computers or workstations that spans a or workstations that spans a relatively small physical area.relatively small physical area.

DefinitionDefinition

CoveredCoveredAreaArea

A single building or group of A single building or group of buildings.buildings.

A city, a country or A city, a country or even the world.even the world.

Network of LANs that Network of LANs that spans a relatively large spans a relatively large geographical area.geographical area.

A comparison of a LAN and a WANA comparison of a LAN and a WAN


A. Wire-based Communications ChannelsA. Wire-based Communications Channels

communications channels that can be found all over the world

1. Telephone Lines1. Telephone Lines

Pairs of insulated Pairs of insulated copper wirescopper wires

Telephone lineTelephone line

Twisted-pair wireTwisted-pair wire

A Twisted-pair cableA Twisted-pair cable


In order to connect to the Internet through telephone lines, we have to use modems.

Internal Modem External ModemInternal Modem External Modem

AppearanceAppearance

PositionPosition

Expansion board Expansion board

Inserted into vacant expansion slots.

Attached to computers through the standard RS-232.

Internal and External Modems


used for cable television and computer network connections

2. Coaxial Cables2. Coaxial Cables

Insulating material

Central wirePlastic outer coating

Woven or braided metal

more expensive than telephone lines, but can transmit much more data at a time


used extensively by telephone companies to rebuild their communications infrastructure

3. Optical Fibers3. Optical Fibers

Data transmitted within an optical fiber

Transmitted as light rays

Signals


Several fibers are bundled into a commonSeveral fibers are bundled into a common sheath to form a fiber cablesheath to form a fiber cable

Opaque plastic protective coating

Transparent core

Light-reflecting cladding layers

Optical Fibers

Layers of moisture barrier sheathing and

impact-resistant plastic jackets

Fiber CableFiber Cable Optical FiberOptical Fiber


Advantages of using optical fibers over Advantages of using optical fibers over telephone lines or coaxial cablestelephone 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


Disadvantages of using optical fibers Disadvantages of using optical fibers over telephone lines or coaxial cablesover telephone lines or coaxial cables

(1) more expensive to install

(2) more easily damaged

(3) more difficult to split


B. Wireless Communications ChannelsB. Wireless Communications Channels

1. Analogue and Digital Signals from 1. Analogue and Digital Signals from Land-based AntennasLand-based Antennas

used for cable television broadcast, inter-urban telephone traffic and so on

Microwave antenna

Signals carried by microwave


Advantages of using land-based Advantages of using land-based microwave antennas over microwave antennas over

telephone lines or coaxial cablestelephone 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


2. Analogue and Digital Signals from 2. Analogue and Digital Signals from Communications SatellitesCommunications Satellites

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


3. Infrared Waves from Infrared Devices3. Infrared Waves from Infrared Devices

used for short-distance remote controls

transmission and reception by invisible band of radiation


4. Radio Waves from Bluetooth Devices4. Radio Waves from Bluetooth Devices

used for short-distance mobile communications

speed is up to 720Kbps data transfer within a range of 10 metres

use omnidirectional radio waves that can transmit through non-metal barriers


State two kinds of wireless State two kinds of wireless

communication channels and compare communication channels and compare

their differences based on the following their differences based on the following

criteria: criteria:

(a) way(a) way

(b) speed(b) speed

(c) limitations(c) limitations


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excellence publication co. ltd. volume 1 2.91 volume 1

Documents

excellence publication

wan slide

network adapters slide

server slide

time slide

network of lans

fast rate slide

twistedpair cable slide