Download Computer Networks An Introduction

Computer Networking
MD. ARIFUR RAHMAN
LECTURER , GOVT. AZIZUL HAQUE COLLEGE,
BOGRA.
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Network Definition

A network can be defined as two or
more computers connected together in
such a way that they can share
resources.

The purpose of a network is to share
resources.
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Network Definition(cont…)
A resource may be:
 A file
 A folder
 A printer
 A disk drive
 Or just about anything else that exists
on a computer.
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Network Definition(cont…)

A network is simply a collection of computers
or other hardware devices that are connected
together, either physically or logically, using
special hardware and software, to allow them
to exchange information and cooperate.
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Computer Networks

A computer network or data network is a
telecommunications network that allows
computers to exchange data.

In computer networks, networked computing
devices pass data to each other along data
connections. The connections (network links)
between nodes are established using either cable
media or wireless media. The best-known
computer network is the Internet.
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Advantages of networking
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Connectivity and Communication
Data Sharing
Hardware Sharing
Internet Access
Internet Access Sharing
Data Security and Management
Performance Enhancement and Balancing
Entertainment
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The Disadvantages (Costs) of Networking
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Network Hardware, Software and Setup Costs
Hardware and Software Management and
Administration Costs
Undesirable Sharing
Illegal or Undesirable Behavior
Data Security Concerns
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Communication system
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Component of Communication
System
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Bandwidth: Data Transmission Speed

Bandwidth in computer
networking refers to the data
rate supported by a network
connection or interface. One
most commonly expresses
bandwidth in terms of bits per
second (bps).
The term comes from the field of electrical engineering, where
bandwidth represents the total distance or range between the
highest and lowest signals on the communication channel
(band). Bandwidth represents the capacity of the connection.
The greater the capacity, the more likely that greater
performance will follow, though overall performance also
depends on other factors, such as latency.
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Types: On the basis of Transfer Rate

1. Narrow Band: 45- 300 bps.eg.
Telegraphy.
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Types: On the basis of Transfer Rate

2. Voice Band: 9600 bps /9.6 Mbps.
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Types: On the basis of Transfer Rate
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3. Broad Band: < 1Mbps.
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Methods of Data Transmission
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1. Asynchronous Transmission-
Transmission & Receive anytime
b) Transmission delay is asynchronous
c) Each character needs a start and one or
two stop bits.
*Parity bit.
a)
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Advantages of Asynchronous Transmission
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Transmission & Receive anytime by
Transmitter & Receiver.
No Primary Storage Device.
Less Installation Cost.
Useful in low data transmission rate-eg.
Internet.
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Disadvantages of Asynchronous Transmission-

Increase cost of as it remain unused.
Comparatively less efficient.
Transmission rate is slow.
Use in-
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Computer to Reader /Keyboard /Printer.
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Methods of Data Transmission
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2. Synchronous TransmissionStore data at Primary Storage Device as
Block of 80 to 132 characters.
Transmission delay time is synchronous.
Send header signal And trailer signal .
Detect errors in data.
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Advantages of Synchronous Transmission
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Comparatively more efficient.
Transmission rate high as transmit data
simultaneously
No time interval between delivering
characters.
Need no Start & Stop Bits.
Less Time.
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Disadvantages of Synchronous Transmission
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Need a Primary Storage Device.
Comparatively costly.
Use inComputer to one or more Computers for
long distance data transmission.
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Methods of Data Transmission
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3. Isochronous Transmission-
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Next version of Synchronous Transmission.
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The transmission delay time approximately 0.
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Use in-
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In Real Time Application Data Transfer.
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Data Transmission ModeA.
Simplex: A
e.g. TV, Radio
B
B.
Half- Duplex: A
e.g. Walky-Talky.
B
C.
Full- Duplex: A
e.g. Mobile, Telephone.
B
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Data Transmission ModeI.
Unicast-Mobile
II.
Broadcast- TV, Radio
III.
Multicast-Video Conferencing
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Data Communication MediaA. Cable:
A. Co-Axial Cable
B. Twisted Pair Cable
C. Optical Fiber
B. Wireless:
Radio wave-10 KHz-1GHz
Microwave-<1GHz
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DIELECTRIC MATERIAL
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Data Communication Media
1.
2.
3.
Cable:
A. Co-axial Cable-
Copper core
Insulator
(Dielectric)
Braided Conductor
4.
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TWISTED PAIR CABLE
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WIRELESS MEDIA
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Radio Wave: 10 KHz-1GHz
Bandwidth-24Kbps
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WIRELESS MEDIA
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Satellite Microwave
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300MHz-30GHz
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WIRELESS MEDIA
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Terrestrial MW
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Line of Sight
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WIRELESS MEDIA
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Transponder
INTELSAT
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How many kinds of Networks?

Depending on one’s perspective, we can classify
networks in different ways

Based on transmission media: Wired (UTP,
coaxial cables, fiber-optic cables) and
Wireless

Based on network size: LAN and WAN and
MAN


Based on management method: Peer-to-peer
and Client/Server
Based on topology (connectivity): Bus, Star,
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Transmission Media
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Two main categories:
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Guided ― wires, cables
Unguided ― wireless transmission, e.g. radio,
microwave, infrared, sound, sonar
We will concentrate on guided media here:
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Twisted-Pair cables:
 Unshielded Twisted-Pair (UTP) cables
 Shielded Twisted-Pair (STP) cables
Coaxial cables
Fiber-optic cables
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Topology ― 3 basic types
•
How so many computers are connected together?

Bus Topology
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Star Topology
Ring Topology
Hub
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Topology
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Bus Topology
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Simple and low-cost
A single cable called a trunk (backbone, segment)
Only one computer can send messages at a time
Passive topology - computer only listen for, not
regenerate data
Star Topology
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Each computer has a cable connected to a single point
More cabling, hence higher cost
All signals transmission through the hub; if down,
entire network down
Depending on the intelligence of hub, two or more
computers may send message at the same time
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Ring Topology

A ring topology connects one host to the
next and the last host to the first. This
creates a physical ring of cable.

Uses a token to pass information from 1 computer to the
other. A token is attached to the message by the sender
to identify which computer should receive the message.
As the message moves around the ring, each computer
examines the token. If the computer identifies the token
as its own, then it will process the information.
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A disadvantage of a token ring is if one Computer is
broken or down, the message cannot be passed to the
other computers.
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Mesh Topology
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The mesh topology is the simplest logical topology in terms
of data flow, but it is the most complex in terms of physical
design.
In this physical topology, each device is connected to every
other device
This topology is rarely found in LANs, mainly because of
the complexity of the cabling.
If there are x computers, there will be (x × (x–1)) ÷ 2 cables
in the network. For example, if you have five computers in
a mesh network, it will use 5 × (5 – 1) ÷ 2, which equals 10
cables. This complexity is compounded when you add
another workstation.
For example, your five-computer, 10-cable network will
jump to 15 cables just by adding one more computer.
Imagine how the person doing the cabling would feel if you
told them you had to cable 50 computers in a mesh
network—they’d have to come up with 50 × (50 – 1) ÷ 2 =
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1225 cables!
Mesh Topology
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Other Topology
FULLY CONNECTED
PARTIALLY
CONNECTED
TREE
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Advantages and Disadvantages of Network
Topologies
Topology
Advantages
Disadvantages
Bus
Cheap. Easy to install.
Difficult to reconfigure.
Break in bus disables
entire network.
Star
Cheap. Easy to install.
Easy to reconfigure.
Fault tolerant.
More expensive than bus.
Ring
Efficient. Easy to install.
Reconfiguration difficult.
Very expensive.
Mesh
Simplest. Most fault
tolerant.
Reconfiguration extremely difficult.
Extremely expensive.
Very complex.
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Hardware, Software and Networks Peripherals
(device)
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Network Interface Card (NIC)
Repeater
Hub
Bridge
Routers
Switch
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Hardware, Software and Networks Peripherals
(device)
Application Gateway
Transport Gateway
Router
Bridge, Switch
Repeater, Hub
TCP/IP Model
Hybrid Model
OSI Model
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Questions
?
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