UNIT 1 :INTRODUCTION TO
NETWORKS
Network Technologies
Introduction : Networking
• A network is a link between two or more computer to
communicate and share resource
OR
• A network is a set of devices connected by media links or
communication channel.
Data Communication [Analog, Digital]
• A word ‘Data’ refers to facts, concept & instruction
presented in any form Data Communication is exchange
of data between 2 devices via same form of transmission
medium such as a wire cable.
Fundamental characteristics of DC
• 1) Deliver :- system must deliver data to correct
destination.
• 2) Accuracy :- system must deliver data
accurately[correctness].
• 3) Timeliness :- system must deliver data in timely
manner.
Components of Data Communication
1. Message
The message is an information or data to be communicated. It is consist of text,
number, sound or video or any combination of his.
2. Sender
The sender is a device that sends the data message. It can be a computer,
workstation, time for handset, video camera and so on.
3. Receiver
The receiver is a device that receives the data. It can be a computer, workstations,
time for handset, video camera and so on.
4. Medium
The transmission medium is physical path by which a message travels from sender
to receiver. It can consist of twisted pair cable, co-axel cable, laser etc.
5. Protocols
A protocol is a set of rules that controls the data. It represents an agreement
between the communicating devices without a protocol two devices may be connected but not
communicating.
Network Application
• Marketing and Sales
• Financial Services
• Electronic mail
• Directory Services
• Information Services
• Teleconferencing
• Cellular Telephone
• Cable Television
Types of Network
1. LAN (Local Area Network):
• A LAN is introducing to connect the computer in a single office,
campus or building.
• A LAN can be as single as two PC or it can extent throughout
company and include voice, sound and video voice.
• The earliest LAN couldn’t cover a great distance.
• LAN is design to allow resources to be shared and exchange
information between personal computer and workstations.
• LAN has data rates in 4 to 16 mbps rate. Today’s speeds are
increasing and can reach 100 mbps or more than data.
• LAN use single cable to which all machine are attached.
• LAN
2. MAN ( Metropolitan Area Network):
• MAN is basically bigger version of LAN.
• MAN is design to extent over and entire city.
• It may be a signal network such as a cable television
network or it may be connecting a number of LAN into a
larger network. So that, resources may be shared LAN to
LAN.
• For ex. A company can use a MAN to connect the LAN in
all of its office throughout a city.
• A MAN support both data and voice.
MAN
3. WAN ( Wide Area Network ):
• WAN provides long distance transmission of data, voice,
image and video information over large geographical area
that may be a country.
• WAN play an important role in the future development of
corporate networks.
• A WAN is comprised of multiple LAN connected to each
other. So that, user and computer in one location can
communicate with user and computer in other location.
4. WLAN ( Wireless Local Area Network):
• Unlike LAN, in WLAN no wire are used but radio signals
are the medium for communication.
• Wireless network cards are used in this type of network.
• Known as WIFI.
WAN:
5. CAN [Campus Area Network]
• Connecting with multiple LAN but smaller then a MAN.
• This kind of network mostly used in large university or local
offices and buildings.
6. SAN [Storage Area Network]
• SAN technology is use for data storage.
• SAN connect a server to a data storage device by using fiber
channel technology.
7. PAN [Personal Area Network]
• PAN is a computer network used by an individual person.
• A mobile computer or cellular phones are example of personal
area network.
Advantages of network
• File sharing
• Software cost and management
• Security
• Resource Sharing
• Communication
• Flexible access
• Faster Problem Solving
• Security through redundancy
• Collaborative process
Disadvantages Of Network
• If server develops a fault user may not be able to run the
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application programs.
A fault in the network can call user to loss of data.
It is difficult to make the system secure from hacker.
As graphics increases on a network the performance
decreases unless it is design properly.
The larger the network becomes fault to manage.
It would take a long time to install software application on
each computer one at a time.
Network Criteria [width / limit]
• Criteria for network includes three things:
1. Performance, 2. Reliability 3. Security
1. Performance:
• Performance can be measurable in many terms including transmit
time and response time.
• Transmit Time: the amount of time required for a message to travel
from one device to another.
• Response Time: Response time is a time between an inquiry and a
response.
• The performance of a network depends on following number of
factors :
1. Number of Users
2. Type of transmission medium
3. Hardware
4. Software
1. Number of users:
The large number of users can slow the response time in a network.
2. Types Of Transmission media:
The medium define the speed at which data can travel through a
connection. If the medium is good than data transfer faster on the
network.
3. Hardware:
A good hardware is also affect on the network in both speed and
capacity of transformation.
4. Software :
The software is used to process data at the sender, receiver and
intermediate node also affect network performance.
2. Reliability [Dependability]
Frequency of failure:
It may possible to occur failure in network. The strong
network is always perform better and take very less time in
failure.
Recovery time of a network after a failure:
How long does it take to restore service? A network that
recovers quickly is more useful than one that does not.
Natural Calamities:
A network must be protected from natural calamities such
as fire, earth quakes, floods etc.
3. Security
Network security includes
unauthorized access and virus.
protecting
data
from
Unauthorized access:
For a network to be useful, sensitive data must be
protected from unauthorized access. So on the network
only authorize person can access the data which provides
much more security.
Virus:
A good network is protected from virus by hardware and
software design
Clients, Servers and Peers
• Three roles for computer in local area network
Client : client computer means user which use the network
but not provide network resources.
2. Servers : Server computer means server which provide
network resources.
3. Peers : Peers computer is the combination of both client as
well as server.
1.
• Base on the roles of the computers, networks are divided into
three types.
• Server Based Network[also called Client-Server]
• Peer Based Network[also called Peer-to-Peer]
• Hybrid Network
Server Based Network
• Server based networks are servers that provide security
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and resource to the networks.
A server based network divided processing clients and
servers.
Clients often send a front-end request service, such as file
storage and printing and servers often send a back end
response which delivers them.
Server computers are more powerful then clients
computers.
In this kind of network user’s information is stored
centrally. So that, user only need to log on once.
• Server Based Network
Advantage of Server based Network:
• Strong central security.
• Central file storage, which allows all the users to work from the same,
set of data and provides easy back up of critical data.
• Ability to share expansive equipment[kit] such as laser printers and
mass storage.
• Easy manageability of a large number of user’s.
• Central organization, which keep data from getting lost among
computers.
Disadvantage of Server based Network:
• Expansive dedicated hardware.
• Expansive network operating system, software and client licenses.
Peer Based Network
• Peer networks are those networks where no
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central
control is available over the network.
There are no server in peer network user simply share
disk space and resource such as printer and faxes.
Because there is no central security, you will have to know
the individual password for each secure shared resource
you wish to access.
Peer networks are organized into workgroups.
When a number of users are accessing resource on a
peer, the user of that peer will decrease performance.
• Peer Based Network
Advantages of peer based network:
• No extra investment in server hardware or software
required.
• Easy setup.
• No network administration required.
• Ability of users to control resource sharing.
• Lower cost for small networks.
Disadvantage of peer based network:
• Additional load on computer because of resource sharing.
• Lack of central organization, which can make data hard to
find.
• Weak security.
Hybrid Network
• Hybrid networks have all three types of computers operating on them.
• This means that while most shared resources are located on servers,
network users still have access to any resources begin shared by
peers.
 Advantage of Hybrid Network
• The advantages of server based networking.
• Many of the advantages of peer based networking.
• Ability of users and network administration to control security based
on the importance of the shared resources.
 Disadvantages of Hybrid Network
• The disadvantages of server based network.
Server Types
• There are many types of server are available.
• Common server types are:
1. File servers
2. Print servers
3. Application servers
4. Massage servers
5. Database servers
• A server in a network which is used to perform specific
task in support of computer on the network.
1. File Servers
• File servers allow networks users to share files.
• File server are the network application that store, retrieve
and move data.
• Users can exchange, read, write and manage shared files
and the data contained[control] in them.
• File servers provides file services like:
a. File transfer
b. File storage and migration[shifting]
c. File update synchronization
d. File archiving[Back up]
A. File Transfer
• Ability to copy and share file across a network.
• When a user transfers a confidential file, they need a
network security.
• Every network operating system has its own level of file
security.
B. File Storage and migration
• Huge amount of data must be storage some where.
• Most storage is made on hard drive.
• Hard drive can be access quickly.
Data Migration:
• The process by which data is moved from online to offline or
near line storage is called Data Migration.
C. File update synchronization
• These services ensuring that user have the latest copy of file.
• File update synchronization service can be managing file by
monitoring the date time stamp on file to determine which file
where save more recently.
D. File Archiving[Backup]
• File archiving is the process of backing up files on offline
storage devices, such as taps or optical disks.
• You can backup all the servers on network onto a single
backup storage.
2. Print Servers
• Print services are network services which control printing and
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fax machine.
Print server allow users to share printers.
Allow you to place printers where convenient.
Allow users to share network fax services.
Achieve better workstation performance by using high speed
network data transfer.
You can place printers anywhere on a network and anyone
network can use anyone of those printer.
From application you can send a document to a fax queue,
which then takes care of the faxing.
With a fax server, you can receive faxes directly on your
workstation.
3. Application Servers
• Application services allows client PCs to access and use
extra computing power and expansive software
application that located on a shared computer or another
computer.
• Application servers may be dedicated to specific
functions. So that, they can take on common tasks for
clients or they can provide file, print, communication and
database services.
4. Message Servers
• Message servers provide massage services in a variety of
communication method then file server. With file servers
data can pass between users only in file from.
• with message services, data can take the from of
graphics, video or audio as well as text and binary data.
• There are four main types of message service:
• a. Electronic Mail
• b. Workgroup Applications
• c. Object-oriented Applications
• d. Directory services
5. Database Servers
• Data services can provide a network with powerful
database capabilities.
• Database servers provide services including security,
database optimization, data integrity, data distribution and
utilization database management system.
• The database application run on two separate
components:
• i. Client-side Application
• ii. Server-side Application
Network Topology
• The way in which the connections are made is called the
topology of the network.
• A topology means a layout of a network.
• Topology can be either of two types:
1.Physical Topology: Which describe how the cable are
run?
2.Logical Topology: Which describe how network message
travels?
1. Physical Topologies
• Physical topologies describe that how the cables are run.
• Physical topologies affected by several factors are:
1. Official Layout
2. Troubleshooting Techniques
3. Cost of Installation
4. Type of Cable used
Types of physical topologies:
1.
2.
3.
4.
5.
Bus Physical Topology
Star Physical Topology
Ring Physical Topology
Mesh Physical Topology
Hybrid Physical Topology
1. The Bus Physical Topology
• All computers on the networks share a single cable and
this cable is typically co-axial cable.
• The bus physical topology is used when a network is
small, simpler or temporary.
• The Cable runs from computer making each computer a
link of chain.
Advantages of Bus Physical Topology
• The bus is simple.
• Reliable in very small network.
• Easy to setup.
• Easy to understand.
• It is less expansive because it require the list amount of cable to
connect the computer together.
• It is easy to extant the bus.
Disadvantages of Bus Physical Topology
• The biggest problem with bus network is that is it is not terminated
correctly, then your network can not transmit properly.
• The network will not transmit correctly if even one node on a network
not work properly because the system depends on every node.
• If the node is active but will not work properly, then problems will
occur.
• The active node will still attempt to process packets or massage but
will do it incorrectly. That’s way the whole network will collapse[fail].
• Cable breaks also create a problem if the cable is damage at some
point and network may not work.
2. The Star Physical Topology
• In the star topology, every server and workstation plugs into a
central hub that provides connections to all other devices
connected to the hub.
• How a Star Network Works?
• Each computer on a star network communication with a central
hub that resend a massage either to all the computers or only
to the destination computer.
• Each node on the network has its own connection to the central
switching point. That is each connection is independent on all
other connections.
• A break in one workstation cable will not affect another
workstation’s connection.
• Diagram
Advantages of Star Physical Topology
• The network is relatively easy to cable.
• It is easy to modify and add rest of the network.
• Single computer failures do not necessarily bring down
the whole network.
• You can use several cable types in the same network with
the hub.
Disadvantages of Star Physical Topology
• If the central hub fails the whole network fails.
• It is costly.
• Each piece[part] of network is required its own cable to
run.
3. The Ring Physical Topology
• In this type of topology, each node is connected to two other nodes
end create a ring.
• The ring physical topology connects all computers on the network in
loop, running double cable between each node in order to maintain
network.
• Each computers is connected to the next computer with the last
connected to the first.
How a Ring Network works?
• Every computer is connected to the next computers in the
ring and each transmits what it receives from the previous
computer.
• The message flow around the ring in one direction. Since,
each computer retransmit what it receives. A ring is an
active network and is not subject to the single loss
problem.
• There is no termination because there is no end to the
ring.
Advantages of Ring Physical Topology
• Because every computer is given equal access to the
token[permission],
no
one
computer
can
monopolized[control] the network
Disadvantages of Ring Physical Topology
• Failure on one computer, all the ring can affect the whole
network.
• It is difficult to troubleshoot a ring network.
• Adding or removing computer upset the network.
DAS : A computer that is connected to both rings is called
Dual Attachment Station [DAS] and one of the rings is
broken by cable fault, computer switches to the other ring,
providing continued full access to the entire network.
2. Logical Topologies
• Logical or electrical topologies describe the way in which
a network transmits information from one node to the next
node.
Types of logical topologies:
1. The Bus Logical Topology
2. The Ring Logical Topology
3. The Mesh Logical Topology
1. The Bus Logical Topology
• The bus logical topology is broad cast system which means
what one station says all station hear.
How does the Logical Bus Topology works?
• A node on the network has data for another node; the sending
node broadcast the data to the entire network.
• Every node on the network hears it and looks to see it the data
is for them. If so, they keep the data. If not they ignore the data.
• On a bus network every workstation can send out information
in a package called a packet.
• When a station has data to send it first listen to the channel.
• If the channel is busy then station waits until it become ideal.
2. The Ring Logical Topology
• The ring topology is used in token ring and Fiber Distributed
Data Interface [FDDI].
How It Works?:
• Every station must repeat what it hears from the previous
station.
• When a piece of data gets back to the originator, it stops.
• An entire file can’t be transmitted in one packets. So, its pieces
will be transmitted.
Token:
• Token is a special frame which contains bit pattern that is
completely different from any other data flow.
• Token is permission for data transmission.
• The ring logical topology is used token packet.
The Ring Logical Topology
• Diagram:
How dose the token packet move around the network?
• If station has data to send it, keep the token and send a
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data frame.
When a workstation is done with token packet, it releases
it to whatever station is next in line.
If nobody keep it, the workstation is released second time.
If nobody response to the token packet for a second time
then the work station stand out a general query known as
a solicit success or frame.
This frame goes out over the network, asking, “Who is
supposed to get the token ring next?”
If a workstation responds, the sending workstation
addresses the token to that workstation and passes the
token.
3. The Mesh Logical Topology
 Mesh Logical Topology
• The mesh topology connects all devices to each other. It allows
communication to continues in the event of a break in any one
connection.
• While the data is travelling network, it is automatically configuration to
reach the destination by talking the shortest roots.
Advantages of Mesh Physical Topology
• A mesh topology is robust. If one link becomes unusable, it does not
affect the entire system.
• Another advantage is privacy or security. When every massage sent,
travels along the dedicated line only the intended recipients it.
Disadvantages of Mesh Physical Topology
• The Devices must be connected to other devices, installation and
reconfiguration are difficult.
• The hardware require to connect each link (input, output ports and cable)
can be very expansive.
Networks Protocols
• Protocols are set of rules that provides way for computers to
exchange information.
• Networks are full of protocols.
• A computer needs to know exactly how message will arrive from the
network. so it can make sure the message gets to the right price.
Hardware Protocol:
• Hardware protocols define how hardware devices operate and the
work together.
Software Protocol:
• Programs communicates with each other via software protocols.
• Network Client Computers and network server computers have
protocol package that must be loaded to allow them to talk to other
computer.
Wireless Network
• A wireless network enables people to communicate and
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access applications and information without wires
A wireless network is a computer network that uses wireless
data connections between network nodes.
Wireless networking is a method by which homes,
telecommunications networks and business installations avoid
the costly process of introducing cables into a building, or as a
connection between various equipment locations.
Wireless telecommunications
networks are generally
implemented and administered using radio communication.
Examples of wireless networks include cell phone networks,
wireless local area networks (WLANs), wireless sensor
networks, satellite communication networks.
Ad-hoc Wireless Network
• A wireless ad hoc network, also known as a wireless
mesh network or mobile ad hoc network (MANET), is a
wireless network made up of radio nodes organized in a
mesh topology.
• Each node forwards messages on behalf of the other
nodes and each node performs routing.
• Ad hoc networks can "self-heal", automatically re-routing
around a node that has lost power.
Sensor Wireless Network
• It works on principle that consist sensor which are
distributed thick and adhoc method.
• This sensor works with each other to senses a physical
phenomenal and then information gather to its process to
get relevant result.
• Wireless sensor network consist of protocol and algorithm
with self organizing capabilities.