Introduction to
Computer Networks
Computer Networks
A system with
● Multiple computers
● Inter Connection
● Share information
● Share resources.
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Usages
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Resource Sharing
Server-Client model
Communication Medium
eCommerce
Form
Example
B2C
Ordering products online
Home Applications
B2B
Manufacturer ordering
materials from Supplier
C2C
Auctioning second hand
product online
G2C
Government Distributing
services online
P2P
File sharing
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Access to remote information
Person-to-person communication
Interactive entertainment
Electronic commerce
● Mobile Users
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Goals
● Resource Sharing
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Many organization has a substantial number of computers in operations, which are
located apart. Ex. A group of office workers can share a common printer, fax, modem,
scanner etc.
● High Reliability
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Inter-process Communication
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If there are alternate sources of supply, all files could be replicated on two or, machines.
If one of them is not available, due to hardware failure, the other copies could be used.
Network users, located geographically apart, may converse in an interactive session
through the network. In order to permit this, the network must provide almost error-free
communications.
Flexible access
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Files can be accessed from any computer in the network. The project can be begun on
one computer and finished on another.
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Line Configuration
Point-to-Point Connection
1.
2.
3.
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5.
6.
Provides a dedicated link between two devices
Entire capacity of the link is reserved
Mostly uses wire or cable to connect
Microwave or satellite links may be used too
Topology is considered to be one of the easiest
The simplest to establish and understand
Multipoint Connection :
1.
2.
3.
4.
Called Multidrop configuration
Two or more devices share a single link
The capacity of the channel is shared
Two possibilities in this configuration:
a.
Spatial Sharing: Can share the link
simultaneously
b.
Temporal (Time) Sharing: Take turns
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Network Topology
The arrangement of a network:
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Comprises of nodes
Connecting lines
The various network topologies are :
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Transmission Modes
The mechanism of transferring of data between two devices connected.
1. Simplex Mode
2. Half duplex Mode
3. Full duplex Mode
one way only
Simplex Mode
Bi-directional but not simultaneously
Half Duplex Mode
Both way and simultaneous
Full Duplex Mode
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Transmission Mediums
Medium through which data from one point to another
Factor to be considered:
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Transmission Rate
Cost and Ease of Installation
Resistance to Environment Conditions
Distances
Mainly Two Types:
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Bounded or Guided Medium
Unbounded or Unguided Medium
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Guided vs Unguided Mediums
Guided Medium
Unguided Medium
Physical Wires are used
Electromagnetic signals are used
High Speed
Less speed
Secure
Less Secure
Used for shorter distances
Used for larger distances
Twisted pair, CAT 5, Fiber optic Cable etc
Radiowave, Microwave, Infrared etc
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Network Hardwares
Network Cable with RJ-45 Connector
Internal Network Card
Distributor
Router
External Network Card
USB Network Card
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Guided Mediums (Coaxial Cable)
Coaxial Cable
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High Bandwidth
Better noise Immunity
Easy to install and expand
Inexpensive
Single cable failure can disrupt the entire network
Two types of cable
○ Baseband
○ Broadband
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Guided Mediums (Twisted Pair Cable)
Unshielded Twisted Pair Cable (UTP)
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Least expensive
Easy to install
High speed capacity
Susceptible to external interference
Lower capacity and performance
Short distance transmission due to attenuation
Bandwidth is low compared with Coaxial Cable
Provides less protection from interference
Used in LAN technologies like Ethernet
Shielded Twisted Pair Cable (STP)
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Better performance at a higher data rate
Eliminates crosstalk
Comparatively faster
Easy to install
Comparatively difficult to manufacture
More expensive
Bulky
Used in telephone lines
Used in Local Area Network
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Guided Mediums (Optical Fiber Cable)
Optical Fiber Cable
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Increased capacity and bandwidth
Light weight
Less signal attenuation
Immunity to electromagnetic interference
Resistance to corrosive materials
Difficult to install and maintain
High cost
Fragile
Used in Backbone networks
Used in some Cable TV companies
Used in Local-area Networks
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Unguided Mediums
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Unguided Mediums (Radio Waves)
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Waves ranging frequency 3 KHz to 1 GHz
Radio waves are omnidirectional
Can penetrate walls
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Useful for multicasting
AM and FM radio, television, maritime radio,
cordless phones, and paging are examples
of multicasting.
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Unguided Mediums (Microwaves)
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Propagation is line-of-sight.
Very high-frequency microwaves cannot penetrate walls.
The microwave band is relatively wide, almost 299 GHz.
Use of certain portions of the band requires permission from authorities.
It is very costly
Types are:
○ Terrestrial Microwave
○ Satellite Microwave
Used for long distance telephone communication
Carries 1000's of voice channels at the same time
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Unguided Mediums (Infrared)
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Frequencies from 300 GHz to 400 THz can be used for short-range communication
Infrared waves, having high frequencies, cannot penetrate walls
Within a wall prevents interference between one system and another
Useless for long-range communication.
We cannot use infrared waves outside a building
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Can be used to transmit digital data with a very high data rate
The Infrared Data Association(IrDA) established standards for using these signals for
communication between devices such as keyboards, mouse, PCs and printers.
Infrared signals can be used for short-range communication in a closed area using
line-of-sight propagation.
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Types of Computer Networks
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Local Area Network (LAN)
Metropolitan Area Network (MAN)
Wide Area Network (WAN)
Personal Area Network (PAN)
Storage Area Network (SAN)
Enterprise Private Network (EPN)
Virtual Private Network (VPN)
Wireless Network
Inter Network (Internet)
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Service Types
Connection Oriented Services vs Connectionless Services
1.
2.
3.
4.
In connection oriented service authentication is needed,
while connectionless service does not need any
authentication.
Connection oriented protocol makes a connection and
checks whether message is received or not and sends
again if an error occurs, while connectionless service
protocol does not guarantees a message delivery.
Connection oriented service is more reliable than
connectionless service.
Connection oriented service interface is stream based
and connectionless is message based.
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Thank You
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References
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https://www.tutorialspoint.com/computer_fundamentals/computer_networking.htm
https://www.geeksforgeeks.org/basics-computer-networking/
https://www.studytonight.com/computer-networks/overview-of-computer-networks
https://www.studytonight.com/computer-networks/uses-of-computer-networks
https://www.studytonight.com/computer-networks/transmission-mode
https://www.studytonight.com/computer-networks/transmission-mediums
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