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WELCOME
TO THE WORLD OF
NETWORK
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What is a network?
A network is a group of computers / electronic devices
that are able to communicate with one another and also
share data, files, programs, and operations.
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Why Network ???
Minimise Duplication
Of Resources
Of Applications/Programs
Of Efforts
Of Data
Make Info/Resource Access Easy
Improve Efficiency & Productivity
Minimise Errors and Delays
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Design Considerations
• Application Requirement
• Present Needs
• Future Needs
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Key Issues
Network Architecture,
Network Management &
Network Security
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Network at Various Levels
Local Area Networks
Campus Networks
Wide Area Networks
Intranets
Extranets
Internet
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LOCAL AREA NETWORK
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LAN Involves
• Two or more computers connected together
• Communication and sharing
• Hardware and software
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Local Area Network (LAN)
Topology
Cabling Systems
Active Electronics
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Topology
Bus
Star
Ring
Mesh
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Bus Topology
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Bus Topology
• Network maintained by a single cable
• Cable segment must end with a terminator
• Extra stations can be added in a daisy chain
manner
• Standard is IEEE 802.3
• Thin Ethernet (10Base2) has a maximum
segment length of 200m
• Max no. of connections is 30 devices
• Four repeaters may be used to a total cable
length of 1000mCLICKTECHSOLUTION.COM
• Thick Ethernet (10Base5) used for
backbones, Limited to 500m
• Max of 100 nodes per segment
• Total of four repeaters , 2500m,
with a total of 488 nodes
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Advantages
• Inexpensive to install
• Easy to add stations
• Use less cable than other
topologies
• Works well for small
networks
Disadvantages
• No longer recommended
• Backbone breaks, whole
network down
• Limited no of devices
can be attached
• Difficult to isolate
problems
• Sharing same cable slows
response rates
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Star Topology
• Like the spokes of a wheel (without the
symmetry)
• Centre point is a Hub
• Segments meet at the Hub
• Each device needs its own cable to the
Hub
• Easy to maintain and expand
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• Advantages
• Easy to add devices as
the network expands
• One cable failure does
not bring down the entire
network (resilience)
• Hub provides centralised
management
• Easy to find device and
cable problems
• Can be upgraded to
faster speeds
• Lots of support as it is
the most used
• Disadvantages
• A star network
requires more cable
than a ring or bus
network
• Failure of the central
hub can bring down
the entire network
• Costs are higher
(installation and
equipment) than for
most bus networks
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Star Topology
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TREE TOPOLOGY
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Tree
A tree topology combines characteristics of bus and
star topologies. It consists of groups of starconfigured workstations connected to a linear bus
backbone cable (See fig.). Tree topologies allow for
the expansion of an existing network, and enable
schools to configure a meet their needs. network to
Advantages of a Tree Topology
Point-to-point wiring for individual segments.
Supported by several hardware and software vend
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Disadvantages of a Tree Topology
Overall length of each segment is
limited by the type of cabling used.
If the backbone line breaks, the
entire segment goes down.
More difficult to configure and
wire than other topologies.
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Ring Topology
• No beginning or end (a ring in fact !!)
• All devices of equality of access to media
• Single ring – data travels in one direction only
Each device has to wait its turn to transmit
• Most common type is Token Ring (IEEE 802.5)
• A token contains the data, reaches the
destination, data extracted, acknowledgement
of receipt sent back to transmitting device,
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Ring Topology
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Ring Topology
Advantages
• Data packets travel
at great speed
• No collisions
• Easier to fault find
• No terminators
required
Disadvantages
• Requires more cable
than a bus
• A break in the ring
will bring it down
• Not as common as the
bus
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Mesh Topology
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Mesh Topology
• Not common on LANs
• Most often used in WANs to interconnect
LANS
• Each node is connected to every other
node
• Allows communication to continue in the
event of a break in any one connection
• It is “Fault Tolerant”
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Mesh Topology
Advantages
• Improves Fault
Tolerance
Disadvantages
• Expensive
• Difficult to install
• Difficult to manage
• Difficult to
troubleshoot
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T
O
P
O
L
O
G
I
E
S
BUS
STAR
HYBRID
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Network in a building
SERVERS
3rd Floor
2nd Floor
Switch
Node
Switch
Node
Switch
Node
1St Floor
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Cabling Systems
 RS 232
 10 Base 2
 10 Base 5
 10 Base T (UTP)
 100 Base T (UTP)
 Fiber Optic
 Use of Structured Cabling
(upgrade,phased,error dect.)
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Active Electronics





NICs
HUBs
Switches
Modems
Routers
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Key Issues in Selection of Electronics
Present Application Requirements
Provision for incorporating Future
Technologies
Cost Consideration
Bandwidth Capacity
Ease of Installation
Ease of fault finding and maintenance
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Campus Networks
Topology
Cabling
Active Electronics
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(Topology)
Campus Networks
Bus
Star
Mesh
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Cabling
(Campus Networks)
Copper
Fiber
Wireless LAN
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Campus Network
CISC O
H A L L
Block 1
Central Block
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Block 2
Active Electronics
(Campus Networks)
Hubs
Switches
Short Range Modems
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Wide Area Networks
PSTN Based Networks
Leased Line Based Networks
VSAT Based Networks
Other Related Network
Methods based on Media like
- Microwave, Radio Etc.,...
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Wide Area Network
(PSTN Based)
PSTN Exchange
Modem
CISC O
Modem
H A L L
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Remote Office
Remote Office
Wide Area Network (Leased line)
Leased Line
Modem
Leased Line
Modem
LEASED LINE
CISC O
H A L L
Remote Office
Central Office
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Wide Area Network (VSAT Based)
Satellite
VSAT
CISC O
VSAT
H A L L
Central Office
Remote Office
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Major Intra-networking
Components
• CABLE
• Physical connection between
workstation
• Hubs/Concentrator
• Rebroadcast the digital signals to all
workstation on LAN
• Network Interface Card
• LAN communications port for each
workstation
• File/LAN Server
• Hosts Internal Network services for
your organisation
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Network Operating Systems
NetWare
Windows NT Server
Unix (Unix variants)
VMS (virtual machine sys)
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Networks can be Interoperable
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Security Considerations:
•
•
•
•
•
Identify and Authenticate Users
Control Access to Systems
Classify Data
Encrypt Sensitive Data
Audit and Monitor Activity
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Do’s & Don’ts in a Network
• Login & Logout
properly
• Regular Back-up of
Data
• Share Resources only to
required Users
• Protect Resources by
Passwords
• Protect Network from
Virus
• Do not allow
unauthorised Access
• Do not leave the
systems in “LOGGED
IN” state
• Do not use systems for
other than required
usage
• Do not tamper with the
Network
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COMPARISON
• Wired
•
•
•
•
•
•
•
•
•
Example
Range
LAN
Ethernet
1-2 km
WAN
IP routing
worldwide
MAN
ATM
250 km
Internetwork Internet
worldwide
Wireless:
WPAN
Bluetooth(802.15.1) 10 - 30m
WLAN
WiFi(IEEE 802.11) 0.15-1.5 km
WMAN
WiMAX(802.16)
550 km
WWAN
GSM,3G phone nets worldwide
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Bandwidth
(Mbps)
10-1000
0.010-600
1-150
0.5-600
0.5-2
2-54
1.5-20
0.01-02
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