Lecture-03 - Introduction To Network.pptx

Introduction To
Network
By Md. Sakhawat Hossain

What is a computer network?
A computer network, or data network, is a digital telecommunications network which
allows nodes to share resources. In computer networks, computing devices exchange data
with each other using connections (data links) between nodes.
 Two or more computers connected together through a communication medium to share
resources is called computer network.

Why is a network needed?
Network is nothing but a medium to transfer message or simply say data.
let us clear this with a real life example,
suppose you are travelling by your car from Dhaka to Khulna, in that scenario the road is a
network and your car is the packet travelling through this network and you of course are the
data enclosed in the packet.

Application
 Sharing of resources such as printers
 Sharing of expensive software's and database
 Communication from one computer to another computer
 Exchange of data and information among users via network
 Sharing of information over geographically wide areas.

Computer Network
There are two types of computers used in computer
network.
 Terminal/Node
The computers, which take part in the activities of the
network, are called terminal or node.
 Server
It is a central computer in a network, which controls
all the terminals of the network. It is used to fulfill all the
requests from terminals.

Advantages of Computer Network

Advantages of Computer Network
 FILE SHARING – Networks offer a quick and easy way to share files directly.
 RESOURCE SHARING – All computers in the network can share resources such as
printers, fax machines, scanners, and modems.
 COMMUNICATION –Those on the network can communicate with each other via e-
mail, instant messages, etc.
 Flexible Access - Networks allow their users to access files from computers throughout
the network.
 Sharing of Information - Computer networks enable us to share data and information
with the computers that are located geographically large distance apart.

Types of Network
Based on the size and the coverage area, networks are categorized into the
following types:
 Personal Area Networks (PANs)
 Local Area Networks (LANs)
 Metropolitan Area Networks (MANs)
 Wide Area Networks (WANs)
 Campus Area Network (CANs)

Personal Area Networks (PANs)
PAN stand for Personal Area Network.
A personal area network (PAN) refers to the interconnection
of information technology devices or gadgets within the
environment of an individual user.
Typically the range lies within 10 meters or 33 feet .
These interconnected devices might include laptop
computers, PDAs, cellphones, printers, PCs or other
wearable computer devices.

Also known as a wireless personal network (WPAN)
Typically uses Bluetooth for connecting devices.
NFC is a newly emerged type of PAN technology.
PANs can be wired, such as USB or FireWire, or they can be
wireless, such as Bluetooth and ultrawideband.

What can personal networks are do?
 Wireless connections between PCs and peripherals can free up
floor space, remove unwanted cables and liberate floor plans.
 Connected Bluetooth devices can automatically synchronize
data downloads and uploads, and exchange information.
 Mobile employees can use Bluetooth-equipped devices to
access office-based peripherals such as printers, if these
support Bluetooth technology.

Advantages and disadvantages:
PANs are efficient, cost-effective and convenient. Some
PANs can interact badly with other wireless networking
technologies using the same radio bands.
Bluetooth networks are relatively secure, but have slow data
rates.
Bluetooth is a short-range solution – up to ten meters - and
is not suitable for wireless connection over larger distances.

Local Area Networks (LANs)
A local area network (LAN) is a network that connects
computers and devices in a limited geographical area such as
a home, school, office building, or closely positioned group of
buildings.
Each computer or device on the network is a node.
LAN connection speeds can be 10 Mbps or 100 Mbps or 1000
Mbps also.
LAN uses Physical Media (Wired).

Advantages of LAN:
The basic LAN implementation does not cost too much.
It is easy to control and manage the entire LAN as it is
available in one small region.
The LAN configuration is very easy due to availability of
required protocols in the Operating System (OS) itself.
It is easy to share common resources such as printers and
internet line among multiple LAN users.

Disadvantages of LAN
LAN covers small geographical area.
Security issues are big concern as it is easy to have access
to programs and data of peers. Special security measures
are needed to stop unauthorized access.
It is difficult to setup and maintain LAN and requires skilled
technicians and network administrators.
In the server based LAN architecture, if server develops
some fault, all the users are affected.

Metropolitan Area Networks (MANs)
 It is relatively larger than LAN and extends across a city
or a metropolitan.
 It is created by connecting two or more LANs located at
different locations in a city.

Advantages of MAN
 It utilizes drawbacks of both LAN and WAN to provide larger
and controllable computer network.
 MAN requires fewer resources compare to
WAN. This saves the implementation cost.
 It helps people interface fast LANs together. This is due to easy
implementation of links.
 It provides higher security compare to WAN.

Disadvantages of MAN:
It is difficult to manage the network once it becomes large.
It is difficult to make the system secure from
hackers and industrial espionage.
Network installation requires skilled technicians and network
administrators. This increases overall installation and
management costs.
It requires more cables for connection from one place to the
other compare to LAN.

Wide Area Networks (WANs)
A Wide Area Network (WAN) is a computer network that covers a large
geographic area such as a country or the world.
One of the most prominent examples of the existing WAN is the Internet.
Transmission Media
Fibre Optic, Microwave transmission and Satellite.

Advantages of WAN:
WAN covers larger geographical area. Hence business offices
situated at longer distances can easily communicate.
Like LAN, it allows sharing of resources, application and software
among distributed workstations or users.
The software files are shared among all the users. Hence all will have
access to latest files.
Organizations can form their global integrated network through WAN.
Moreover it supports global markets and global businesses.

Disadvantages of WAN
Initial investment costs are higher.
It is difficult to maintain the network. It requires skilled technicians and
network administrators.
There are more errors and issues due to wide coverage and use of
different technologies. Often it requires more time to resolve issues due
to involvement of multiple wired and wireless technologies.
It has lower security compare to LAN and MAN due to wider coverage
and use of more technologies.

DISTINGUISH BETWEEN LAN-WAN-MAN
PARAMETERS LAN WAN MAN
Ownership of network Private Private or public Private or public
Geographical area
covered
Small Very large Moderate
Design and
maintenance
Easy Not easy Not easy
Communication
medium
Coaxial cable PSTN or satellite links
Coaxial cables, PSTN,
optical fibre, cables,
wireless
Bandwidth Low High moderate
Data rates(speed) High Low moderate

Campus Area Network (CANs)
 The campus area network is made up of an
interconnection of LAN with limited
geographical area.
 Network equipment such as switches,
routers and the transmission media i.e.
optical fibre etc are almost entirely owned
by the campus owner.

HOW ARE NETWORKS CATEGORIZED?
Networks are usually classified using three properties:
 Architecture
 Topology
 Protocol

CLASSIFICATION OF NETWORK ARCHITECTURE
The architecture of a network is a logical design that determines how the devices in the
network communicate.
The commonly used architectures for computer networks are:
 Client-server architecture
 Peer-to-peer architecture
 Hybrid architecture

 Client-server Architecture
 On a network built using the client-server architecture, the
devices communicate to other devices through a central
computer referred to as a server.
 The server is a terminal with high processing power, which
provides services for the other computers on the network.
 The client is a terminal that accesses the resources available
on a server.

 Client-server Architecture

 Peer-to-peer Architecture
 On a network built using the peer-to-peer architecture, no
specific distinction exists between a client and a server.
 Any node can provide a service as well as send a request
for a service from another node on the network.
 The peer-to-peer network architecture allows sharing of
resources, data, and users.
 Each node on the network has full control over the network
resources.

 Peer-to-peer Architecture

 Hybrid Architecture
 A hybrid is a composition of two different types of elements.
 A hybrid network architecture is created to get the benefits of both, the peer-to-peer
and the client-server architectures, in a network.

NETWORK TOPOLOGY
The pattern of interconnection of nodes in a network is called the Topology.
The physical topology of a network refers to the configuration of cables, computers
and other peripherals.
The different types of network topologies that can be used to set up a network are:
 Bus Topology
 Ring Topology
 Star Topology
 Mesh Topology
 Hybrid Topology

BUS TOPOLOGY
 The bus topology has each node connected to a main
communication channel.
If one node is faulty this has no effect on the rest of the
network
 If the bus is faulty, the whole network is “down”
Advantage = Easy to add new stations
Disadvantage = Each node may have to compete with each
other in order to transmit and receive data

RING TOPOLOGY
Signals are sent around the network from node to node.
 Data travels in one direction.
 If one of the nodes on the network stops, the entire
network stops functioning.
 If a communications channel fails, the network fails.

STAR TOPOLOGY
 All peripheral nodes are connected to a central node.
 If a peripheral node fails it has no effect on the network.
 If the central node fails the whole network is “down”.
Advantage = Easy to add new stations
Disadvantage = Central node may get congested with
network traffic

MESH TOPOLOGY
 Each node is connected to more than one node.
 This provide an alternate route mechanism.
 Supports back-up and rerouting.
This type topology generally use in military area.
Advantage = A node failure has no effect on the rest
of the network.
Disadvantage = Expensive to set up with a lot of
cabling.

HYBRID TOPOLOGY
The hybrid topology can be a combination of two or more basic topologies, such as bus,
ring, star, mesh, or tree.
 Hybrid networks combine more than two topologies, which, in turn, enable you to get
advantages of the constituent topologies.

Difference
Bus Topology Ring Topology Star Topology
Structure there is a single
central cable (backbone)
and all computers and
other devices connect to it
all computers and other
devices are
connected in a circle
there is a central host and
all nodes
connect to it
Host existence depends on network
needs
depends on network needs yes
Connection
between nodes
It has no connection
between the nodes.
yes no
Host failure network can still run network will fail network will fail
Node failure network can still run network will fail network can still run
Ease of
troubleshooting
difficult. Need to
search for the
problematic node one by
one
depends on backbone. If there is
a backbone, troubleshooting is
difficult. If there is no backbone,
the focus is on the two nodes
not communicating
depends on the host. It is
easier to repair the
problematic host. However, if
the nodes fail, then each
node has to be searched
Ease of adding
or removing nodes
easy difficult average
Number of nodes
when extending
network
many limited limited

NETWORK PROTOCOLS
A network protocol defines rules and conventions for communication
between network devices.
Protocols specify interactions between the communicating entities.

NETWORK PROTOCOLS
TCP (Transmission Control Protocol)
IP (Internet Protocol)
HTTP (Hyper Text Transfer Protocol)
FTP (File Transfer Protocol)
HTTPS (Hyper Text Transfer Protocol Secure)
Network Protocol has five types-

NETWORK PROTOCOLS
File transfer protocol (FTP) – used to transmit files.
Simple mail transfer protocol (SMTP) – used to transmit e-mail messages.
Post office protocol (POP) – allows the recipient to retrieve messages.
Wireless application protocol – enables wireless devices to access and use the
Internet using a client/server network.
802.11 – protocol for wireless LAN technology

Lecture-03 - Introduction To Network.pptx

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