What do you mean by Computer Networks? What are the uses Computer Networks?

And applications of computer networks ?

Ans. Computer Networks

Computer network means an interconnected collection of autonomous computers

that can share and exchange information.

Two computers are said to be interconnected if they are able to exchange information.
Autonomous means that these computers are capable of working independently. It
means that there is no master and slave relationship and all computers are equal and
free to act independently.

Computer network is an interconnection of various computers to share software,

hardware and data through a communication medium between them. It can also be a
collection of computers, printers and other equipment, which are connected together
so that they can communicate with each other.

Uses of Computer Networks

A computer network is useful in the following ways:

1. Network for Companies

2. Network for People

1. Network for Companies

Many organizations have a huge number of computers in operation, generally located

far off positions. Each of these computers may work in isolation from others. But at
some point, these computers in hundreds of locations spread worldwide may need to
transport information, extract and correlate information and then process this
information to examine the current status of the entire company. It is the networks
that make it possible.

Computer networks are useful to the organization for:

• Resource sharing

• High reliability

• Saving money

• Providing a powerful communication medium.

 2. Network for People

A computer network provides a powerful communication medium among widely

spread people. Starting in 1990’s, the computer network began delivering services to
the private individuals at home. An individual can log on to one machine, submit jobs,
move files around and handle network personally.

People may personally use computer network for home shopping, e-banking, e-
mailing, online gaming, social media, video-conferencing or even posting a message
to the worldwide newsgroups. Computer networking is also used for participation in
live TV programmes, communication and entertainment.

Thus computer networks offer following services to an individual:

• Access to remote information

• Person to person communication

• Resource sharing

• Interactive entertainment

• Exchanging information

Applications of Computer Networks

Some of the applications of computer network are the following:

1 Communication Medium

3. Sharing
4. Access to Remote Database
5. Information Services
6. Financial Services
7. Entertainment
8. Marketing and Sales
9. Tele Conferencing
10. Business Applications
1. Communication Medium

The most widely used network application is its use as a communication medium. It is
possible for everyone to send and receive e-mails.

2.Sharing:-A major application of network is that it facilitates distinct types of sharing:

• Sharing of peripherals: It facilitates sharing of Computer peripherals. For example,
each computer on the network need not have laser printer. Through network all users
can access the one in a cost effective manner.

• Sharing of data and information: In a business, several departments working

together, share information or data by interconnecting their networks. Users of a
multi-user system can share and exchange information in an easy manner.

3.Access to Remote Database:-Another area of network application is access to

remote database. Airline reservation, hotel booking, railway reservation etc. are easy
for anyone sitting anywhere in the world. Computer network allows access to a
remote database for a writer’s aid like dictionary, thesaurus, quotations and
encyclopedia. Information on any field can be accessed.

4.Information Services:-There may be corporate information systems such as

marketing information system, customer information system, product information
system etc. Stock market information system allows searches for stocks. Computer
networks also facilitate decision making.

5.Financial Services:-Financial services depending on computer networks include

foreign exchange and investment services, electronic funds transactions (EFT) etc.

6.Entertainment:-Entertainment applications include video on demand, interactive

films and games, live television where audience participate in quiz shows etc.

7.Marketing and Sales:-Computer networks are used extensively in both marketing

and sales organizations. Marketing professionals use them to collect, exchange and
analyze data relating to customer needs. Sales applications include order-entry, order
processing and online system for investment.

8.Tele Conferencing:-Tele conferencing allows conferences to occur without the

participants being in the same place.

Q Explain network topologies in detail ❔

Network Topology

Network Topology refers to the physical or logical layout of the network. It can be
determined by the configuration of connections between nodes. A node is an active
device connected to the network like a computer or a printer.

Network topology means the geometrical arrangement and connection of nodes in the
network. The path taken by data from sender to receiver computer mainly depends
upon the topology of the network. The way how thecomputer is linked to the network
is different in different topologies.

Various Types of Network Topologies

Various types of network topologies are as follows:

1. Bus Topology
2. Star Topology
3. Ring Topology
4. Tree Topology
5. Mesh Topology

1. Bus Topology

In bus topology, all devices on network are connected to a single continuous cable
called a bus. This long cable acts as a backbone to link all the devices in a network.
This cable has terminator at each end. Bus topology uses multipoint cabling i.e.
multiple devices are connected by means of connectors or drop cables. The following
figure shows bus topology:-

A bus topology is the simplest network configuration. Bus is passive topology because
it requires termination. Since the bus is passive topology, the electrical signal from a
transmitting computer is free to travel the entire length of the cable. Network

nodes have unique addresses. Transmission from any station travels the length of the
bus in both directions and can be received by all other stations. The destination
device, on identifying the address on the data packet copies the data onto its disk and
frees the line.

Advantages of Bus Topology

• The main advantage of this method is the reduction in physical lines.

• A wide range of equipment can be attached to the LAN without any problem.

• A new node can be added to the LAN without disturbing the network and other
nodes.

• It is easy to use and understand, reliability is higher in very small networks.

• Low cabling cost because of short cable length to be used. Thus it is cheaper than
other topologies.
Disadvantages of Bus topology

• The performance may decrease as numbers of nodes are increased.

• Failure of backbone / main cable affects failure of all devices on the network.

• Each connection between two cables weakens the electrical signals.

• Low reliability. A break or short circuit in the cable can halt the whole network.

• Terminators are required at both ends of the backbone cable.

2.Star Topology:-In a star topology, a device known as hub is placed in the center of
network and all nodes are connected to the central hub and communicate through it
as shown in the figure.

Thus:-

• In some networks when communication goes through a center point, then star
topology is preferred.

• A star network consists of several devices connected to one centralized computer.

• Any communication between the stations must pass through the central node.

Advantages of Star Topology

• In this topology, there is minimum data traffic along the cable and thus it provides
the optimum performance.

• A broken connection between a node and a hub does not affect the rest of the
network.

• Networking management is easy.

• Fault detection is easy.

Disadvantages of Star Topology

• More cabling is needed as compared to Bus or Ring topology.

• The system depends on HUB / central node. If it breaks down, the whole network
would break down.

• More expensive than bus topology.

• The maintenance costs may be high.

2.Ring Topology:-In ring topology, all nodes are connected in a circular form like a
chain, with each node connected to the next. The last node of the network connects to
the first node to complete the ring.

Advantages of Ring Topology

• The ring topology has advantage over bus topology as there is no danger of data
collision.

• Link failure can be easily found as each device is connected to its immediate
neighbours only.

• Moderately simple to install and reconfigure.

• Ring network offers reliable performance for small and larger distances.

Disadvantages of Ring Topology

•There may be large communication delays as the number of nodes increases.

•Each node on the ring must handle the data being transferred by other nodes.

• If one node fails to handle the transfer of data then whole of network fails.

• Because of the closed loop, adding a new node can be difficult.

3.Tree Topology:-A tree topology combines characteristics of bus and star topologies.
It consists of groups of star-configured workstations connected to a linear bus
backbone cable. In a tree network, each device is connected to its own port on a HUB
in the same way as in a star topology. However HUBs are connected together in a
hierarchical way, ie, a HUB will connect to a port on another HUB.

Advantages of Tree Topology

• A tree structure facilitates functional grouping. For example, one branch may
contain all the general ledger terminals, another branch may have all the accounts
receivable terminals and so on.

• It is easy to add new nodes or branches to it.

Disadvantages of Tree Topology

• Data movement through this network can be slow.

• If backbone line breaks, entire network goes down.

• More difficult to configure than other topologies.

5.Mesh Topology

Mesh topology is a network in which every node has a dedicated point-to-point link to
all the nodes within network. There is no chance of data failure, i.e., if one connection
goes down, there are other ways to route the data to its destination.

Advantages of Mesh Topology

• Communication between nodes is very fast.

• It is very reliable because breakdown in any one of the lines will not affect other
links.

• It permits any two devices in the network to communicate directly.

• Privacy or security is maintained because when every message sent travels along
dedicated line, only the intended recipient sees it.

#Disadvantages of Mesh Topology

• To add a new node will increase the cost multiple times depending upon the total
existing nodes in the network.

• Difficult to install and reconfigure.

• Each node having physical links to every other node in the network makes it very
costly.

• Complexity increases as number of nodes increases.

Q.What are analog and digital signals? Also discuss analog and digital transmission.
Write two ways in which they differ ❔

Ans. Analog Signals

An Analog signal is any continuous signal for which the time varying feature (variable)
of the signal is a representation of some other time varying quantity, i.e., analogous to
another time varying signal. It differs from a digital signal in terms of small
fluctuations in the signal which are meaningful.

The analog signals are represented by a sine wave. The signal from a point A to a point
B can have many values. This means, the amplitude of the wave can take many values.

Value

Time
Sine Wave

For example, human voice produces analog signals. Analog signals are affected by the
noise signals Amplifiers are used to boost up the signals. However, amplifiers do not
only boost up the signals but also amplify the noise which deteriorates the signal
quality.

Digital Signals

A digital signal uses discrete (discontinuous) values. By contrast, non-digital (or

analog) systems use a continuous range of values to represent information. Although
digital representations are discrete, the information represented can be either
discrete, such as numbers or letters, or continuous, such as sounds, images, and
other measurements of the continuous systems.

Analog Transmission

Analog transmission is a method of conveying voice, data, image, signal, or video

information. It uses a continuous signal varying in amplitude, phase, or another
property that is in proportion to a specific characteristic of a variable.

#Digital Transmission

Digital transmission is a literal transfer of data over a point to point (or point to
multipoint) transmission medium-such as copper wires, optical fibres, wireless
communications media, or storage media. The data that is to be transferred is often
represented as an electro- magnetic signal (such as a microwave).

Digital transmission transfers messages discretely. These messages are represented

by a sequence of pulses via a line code. However, these messages can also be
represented by a limited set of wave forms that always vary. Either way, they are
represented using a digital modulation method.

Difference between Analog & Digital Transmission

Following are the main differences between anaog and digital transmission:-

Analog Transmission

1. In case of analog communication, it is difficult to remove the noise once added

to the signal. Thus, analog signals cannot perform high quality data
transmission.
2. Analog communication provides less security to messages than the digital
communication.
 3. Analog transmission needs narrower bandwidth.
4. Analog signal transmission requires a band-pass channel.
5. To retransmit the signal AMPLIFIERS are used every 2 to 3 Kins apart.

Digital Transmission

1. In case of digital communication, at the receiving end this additive noise can be
eliminated to great extent easily resulting in better recovery of actual signal.
2. Digital communication provides better security to messages than the analog
communication. It can be achieved through the various coding available
techniques in digital communication.
3. There are various digital communication techniques that use the available
bandwidth much efficiently than analog communication techniques.
4. Digital signal transmission requires a low-pass channel.
5. To retransmit the signal REPEATERS are used every 5 to 6 Kms apart. So,
definitely digital communication is cheaper.

Q.How does digital transmission work? How this transmission is superior to the analog
data transmission ❔

Ans. Digital Transmission

Digital transmission is a literal transfer of data over a point to point (or point to
multipoint) transmission medium such as copper wires, optical fibres, wireless
communications media, or storage media. The data that is to be transferred is often
represented as an electro- magnetic signal (such as a microwave).

Digital transmission transfers messages discretely. These messages are represented

by a sequence of pulses via a line code. However, these messages can also be
represented by a limited set of wave forms that always vary. Either way, they are
represented using a digital modulation method.

Digital signals can be used to propagate both analog and digital data. The process at
the sending and receiving end nodes for digital signal transmission is explained below:

At the sending node,

• Analog or digital data is first converted into a digital binary bit stream through the
process of encoding. If it is analog data, then the encoding process involves an A/D
(analog to digital conversion) process, using devices known as codecs. If data is
already in digital form, then the encoding process just converts the digital data into a
binary stream of Os and 1s (e.g ascii encoding used to encode a text file or an
electronic mail into a binary stream.

At the receiving node,

• The stream of binary digits is then converted back to either analog or digital data, by
using a decoder, that does the reverse operation as that of the encoder used at the
sender.

Following points explain why digital transmission is superior to the analog data
transmission:-

• The main advantage of the digital signals over analog signals is that the precise
signal level of the digital signal is not vital. This means that digital signals are fairly
immune to the imperfections of real electronic systems which tend to spoil analog
signals.

• Digital signals can be encrypted so that only the intended receiver can decode it (like
pay per view video, secure telephone etc.)

• It enables transmission over a long distance.

• Transmission is at a higher rate and with a wider broadband width.

• It is more secure than analogue transmission.

• It is also easier to translate human audio and video signals and other messages into
machine language.

•There is minimal electromagnetic interference in digital technology.

•Digital signal enables multi-directional transmission simultaneously.

Discuss LAN, WAN and MAN on the basis of architecture and geography

Ans. Network Categories or Types of Networks

On the basis of the size of geographical area a network can be divided into three
categories. These three types of networks are:

A. LAN (Local Area Network)

B. WAN (Wide Area Network)

C. MAN (Metropolitan Area Network)

A.Local Area Network (LAN)

A LAN refers to two or more up to several hundred computers and variety of computing
equipment, linked via some communication lines, to exchange information speedily,
within a small well-defined area.

For example, local network area in the University Campus, Industry, Small Town,
Building etc. are local area networks.

The software controlling the network is called the network operating system. LAN
allows access to various resources like printers, scanners, storage capacity and
expensive softwares without actually owning them. It is very economical as a set of
resources can satisfy the needs of many users.

Characteristics of LANs

LANs are not rigidly defined but they share all of the following characteristics:

1.Small Area:-Area covered by a LAN is small. Generally it spans a diameter of not

more than a few kilometers. More commonly it is used inside a single building.

2.Single Owner:-The LAN equipment is generally owned by a single organization such

as a company, a department or a workgroup.

3.Reliability and Stability:-There are permanent links via wires, cables, fiber optics
that transmit data rapidly and give good reliability and stability.

4.Physically Secured:-Generally the LAN is located on the premises of a company or

other organization, so it is physically protected from malicious outsiders.

5.Low Cost Data Transmission:-Due to the inexpensive cable media there are low cost
data transfers at high bandwidth.

Advantages of LANS

1.Better security:-Most network devices, including routers, have built in security

features like firewalls etc. which makes them a much safer way to get users online.

2.Sharing resources:-The primary advantage of a LAN is that it allows sharing of data

and programs. It also allows access to resources like files, application software,
printers, computing power, moderns and fax machines.

3.Productivity Tool:-It offers as a productivity tool. In a business, a LAN is a visible

contributor to increased profitability.

4.High speed exchange:-LAN allows high speed exchange of important information

among people in an organization.
Disadvantages of LANS

1.Costlier:-Sometimes local area network costs higher in comparison with other

alternatives. If one plans to use a network to share a laser printer, the user might find
it cheaper to purchase another printer than to purchase today’s networking hardware
and software.

2.Requires security system:-As data is shared, there is greater need for security
Special security measures are needed to stop users from using programs and data
that they should not have access to. Thus some type of security system is must to
protect private data

3.Adds complexity:-It adds complexity to the computer operations.

4.Lacks one’s hold:-Some control on the part of the user is lost. One may have to share
a printer with other users. One may face a situation like entire network suddenly
locked because one user has made a mistake.

5.Requires technical and administrative skills:-Networks are difficult to set up. Also
networks can be complicated to maintain. Thus installing and managing a LAN
requires technical and administrative skills.

B. Wide Area Network (WAN)

Wide area networks connect computers and smaller networks to large networks over
greater geographic areas, including different continents. These computers may be
linked by means of cables, optical fibres or satellites. WANs are broadband usually
public access networks. WAN came into existence in late 1960s.

Characteristics / Features of WAN

The main characteristics or features of WAN are as follows:-

1.Physically exposed :-Communication channels between the computers are

furnished by public networks which are relatively exposed However, the fact that
many subscribers share those channels which help to protect the privacy of any one
subscriber.

2.Centralizing information:-It is convenient for a business to centralize national

information. This mode of communication allows a business to effectively carry out its
daily functions regardless of location.

3.Remote access:-WAN allows users to engage in real time communication with other
users and provides full time remote resources connected to local services.
4.Permanent wiring not necessary:-Another characteristic of the WAN is that a
connection to it may not be permanently wired, as with a cabled LAN.

Functions of WAN

Following are the main functions of WAN:

1.Remote Data:-The data of sales and transactions at the point-of-sale terminal can
be sent using WANs. The data can be centralized in a computer for processing or
reporting purpose. For example, Super markets in advanced countries connected
through WANs can send all sale data from their remote centers and the central
purchase and distribution center can monitor daily sale figures.

2.Research Project Entry:-Students at remote colleges and Universities may write and
execute their own programs on a central computer. For example, in all IITs connected
through WANs the research projects can be implemented easily because a program
developed at one of IIT’s can be used online by the students of other Its and
duplication of efforts can be avoided.

3.Facilitating Communications:-Corporations in different countries use WANs to

facilitate employee communications, to save on long-distance phone calls and letter
writing and to overcome the time loss involved in overseas communications.
Computer conferencing, in which users communicate with each other through their
computer systems is another use of WANs.

C. MAN (Metropolitan Area Networks):-A network that expands into a metropolitan

area and exhibits high data rates, high reliability and low data loss is called a
metropolitan area network (MAN).

In between the LAN and the WAN is the MAN. A MAN is a netwon that covers an entire
city, but uses LAN technology tes at a higher speed and it is smaller than WAN

Characteristics / Features of MAN

The main characteristics or features of MAN are:

1.Intermediate size:-The MANs interconnect users in a geographic area or region larger

than that covered by a LAN but smaller than the area covered by a WAN.

2.High speed network:-A MAN often acts as a high speed network to allow sharing of
regional resources.

3.Interconnects LANs:-The MANs are also used to interconnect several LANs by

bridging them with backbone lines.
4.Connects whole city:-Metropolitan area networks are quite capable of supporting
entire metropolitan areas. The typical MAN is a high performance, public network.

Q.Draw and explain the TCP/IP protocol architecture and compare it with OSI model ❔

Ans. TCP/IP Reference Model

The TCP/IP, i.e., Transmission Control Protocol / Internet Protocol is the protocol that
makes possible the communication between different types of machines on different
types of networks.

It was developed by the United States Development of Defence Advanced Research

projects Agency (ARPA).

ARPA originally created TCP / IP to connect military networks together.

It was designed with following goals:-

•The network should connect multiple network together.

•The connection should withstand till the source and destination machines are
functioning.

• The architecture should be so flexible that it should be able to transfer data among
different hardware and/or software platforms.

It is the most widely used protocol for interconnect computers and it is the protocol of
the Internet. The operation of the Internet can be described in terms of a number of
layers and protocols. The particular collection of layers and protocols that describe
the operation of Internet is formally known as the TCP / IP Reference Model. TCP / IP
model is normally considered to be a four layer system. Layers of TCP/IP are:

• Application layer

•Transport Layer

•Internet Layer

• Host to Network Layer

TCP/IP Reference Model

Application Layer

Transport Layer
Internet Layer

Host to network Layer

Application layer contains all the useful application protocols. This layer in TCP/IP can
be equated with the combination of session, presentation and application layer of the
OSI reference model.

The transport layer Is primarily concerned with how to transfer the information from
application onto the internet.

Use, purpose and functions of various layers, in detail. Are given below:

1.Application Layer:- This is the highest-level layer in the TCP IP model which is on the
top of the transport layer. This layer includes all processes and services that use the
transport layer to deliver data. The protocols contained in this layer are:

• TELNET: It is the Network Terminal Protocol which allows a user on one machine to
log onto a distant machine and work there.

• FTP: File Transfer Protocol provides a way to transfer files efficiently from one
machine to another

• SMTP: Simple Mail Transfer Protocol delivers the electronic mail.

• DNS: Domain Name System for mapping host names onto their network addresses.

Many other protocols have been added to these, over the years such as NNTP, HTTP
etc. NNTP is the protocol for moving USENET news articles around and HTTP for
fetching pages on the World Wide Web.

2.Transport Layer:-Transport layer provides end-to-end transfer service. It is the layer

above the internet layer in the TCP / IP model. It is designed to allow peer entities on
source and destination machines to communicate with each other. Just as in the OSI
transport layer. Two end-to-end transport protocols have been defined here. These are
Transmission control protocol (TCP) and User Datagram Protocol (UDP). Application
programs send data to the transport layer protocols TCP and UDP. An application is
designed to choose either TCP or UDP based on the services it needs.

• TCP: TCP provides a reliable flow of data between two communicating machines. It
is a connection oriented protocol. It divides the data passed to it from application
layer into suitable sized messages (data blocks), which are passed down one by one to
the internet layer for transmission. At the destination side, the receiving TCP
reassembles the received data or messages into the output format. TCP also handles
flow control. It synchronizes between fast sender and slow receiver.

• UDP: User Datagram Protocol is an unreliable, connectionless protocol for

applications. It just sends packets of data called datagram from one host to the other
but without guaranting that the packet or datagrams reach the other end. The relation
of the protocols is shown in the figure:

3.Internet Layer:-The internet layer provides the means through which a host can send
packets onto a network and then have them travel independently to their destination.
The internet network level protocols IP (Internet Protocol), ICMP (Internet Control
Management Protocol) handle machine to machine communications. These protocols
provide for transmission and reception of transport requests and handle network level
control.

The primary protocol used to move data is the Internet Protocol (IP), which provides
the following services:

Addressing: Determining the route to deliver data to the destination host.

• Fragmentation: Breaking the message into pieces if an intervening network can’t

handle a large message.

Hence packet routing is primarily the main purpose of this layer.

4.Host to Network Layer:-This layer is also called network interface layer. The tasks
performed by this layer are matched with the tasks performed by physical layer and
data link layer of OSI

Model. Host to Network layer cannot define any protocol. It is responsible for
accepting and transmitting IP datagrams. It may consist device driver in operating
system and corresponding network interface card in the computer.

Similarity between OSI Reference Model and the TCP/IP Model

Following points explain the similarity between the OSI reference model and TCP/IP
model:

• Both the models share the similar or equal architecture and it can be defined by the
fact that both of them are constructed with layers.

• Both models share a common ‘application layer’. However, this layer contains
different services, which depends upon each model.
• Both the models have comparable ‘transport’ & ‘network’ layers. Whatever functions
are performed between the presentation and network layer of OSI.

Q.What is a protocol? Discuss the various types of protocols

Protocol

The term protocol is used to refer to a well-known set of rules and formats to be used
for communication between processes in order to perform a given task.

A protocol Is the special set of rules that end points in a telecommunication

connection use when they communicate.

A protocol Is a standard way that specifies a common language which two computers
use to exchange messages. For example, a protocol specifies the exact format and
meaning of each message that a computer can send.

Types of Protocols / Classification of Protocols:-

Protocols are of two types:

A .Communication Protocols

B .Service Protocols

A.Communication Protocol:-

Communication protocols are the formal descriptions of digital message formats and
rules. They are required to exchange messages in or between computing systems and
are required in telecommunications.

Communication protocols cover authentication, error detection and correction, and

signalling. They can also describe the syntax, semantics, and synchronisation of
analog and digital communications. Communication protocols are implemented in
hardware and software.

Popular communication protocols include:

1.Address Resolution Protocol (ARP)

2.Simple Mail Transfer Protocol (SMTP)

3.Internet Message Access Protocol (IMAP)

4.Reverse Address Resolution Protocol (RARP)

5.Multi-Purpose Internet Mail Extension (MIME)

6.Post Office Protocol (POP)

7.Internet Control message Protocol (ICMP)

1.Address Resolution Protocol (ARP):-One of the basic communication protocols is

the ARP. ARP resolves the IOP addresses used by various networking devices into
network usable format used by LANS. ARP serves two basic services to the clients; it
obtains the media control address for the requesting device and records the Media
Access Control (MAC) address in a table called the ARP cache for the future Use.

2.Reverse Address Resolution Protocol (RARP):-A RARP server maintains a database of

machine numbers in the form of an ARP table (or cache) which is created by the
system administrator. In contrast ty ARP, the RARP protocol provides an IP number to a
requesting hardware address. When the RARP server receives a request for an IP
number from a node on the network, it responds by checking its routing table for the
machine number of the requesting node and sending the appropriate IP number back
to the requesting node.

3.Simple Mail Transfer Protocol (SMTP):-The Simple Mail Transfer Protocol is the
standard e-mail protocol of the Internet. SMTP is the standard protocol for sending
emails across the Internet.

It Is a set of communication guidelines that allow software to transmit email over the
Internet. Most email software are designed to use SMTP for communication purposes
when sending email and it only works for outgoing messages.

4.Multi-Purpose Internet Mail Extension (MIME):-

MIME stands for Multi-purpose Internet Mail Extension. MIME is a supplementary

protocol to SMTP that allows non-ASCII data such as binary files, sound files, video
files, etc., to be included in the message (mail) through SMTP and send it over the
internet.

5.Internet Message Access Protocol (IMAP):-Internet Message Access Protocol (IMAP)

is a standard protocol for accessing e-mail from your local server. IMAP is a client /
server protocol in which e-mail is received and held by Internet server. IMAP performs
the same basic functions as POP but can also perform additional features.

6.Post Office Protocol (POP):-Post Office Protocol (POP) is responsible for obtaining e-
mail from the mail server. To send to or collect mail from a remote server, another
protocol called Post Office Protocol (POP) is used. POP requires that the mail server
undertakes one of the following actions:

A)Retrieve mail from the mail server and subsequently delete it from the server.

b) Retrieve mail from the server but not delete it.

c) Not retrieve mail, by simply ask whether new mail has arrived.

7.Internet Control Message Protocol (ICMP):-The ICMP is used by IP and higher-level

protocols to send and receive status reports about information being transmitted.
Routers commonly used ICMP to control the flow, or speed, of data between
themselves. Sometimes the flow of data may be too fast for a router. The router then
requests other routers to slow down.

C.Service Protocol

These protocols provide services to other computers They can be of the following
types:

1.Transmission Control Protocol (TCP)

2.Internet Protocol (IP)

3.User Datagram protocol (UDP)

4.Hypertext Transfer Protocol (HTTP)

5.Telnet

Q.What do you mean by cryptography?

Ans. Cryptography

Cryptography refers to the tools and techniques used to make messages secure for
communication between the participants and make messages immune to attacks by
hackers.

The word cryptography has come from a Greek word which means secret writing. For
private communication through public network, cryptography plays a very crucial role.

The role of cryptography can be illustrated with the help of a simple model of
cryptography as shown below:

Plaintext
Encryption

Medium

Decryption

Plaintext

Ciphertext

(Cryptography Model)

Within the context of any application-to-application communication, there are some

specific security requirements, including:-

• Authentication: It is the process of proving one’s Identity. Primary forms of host-to-

host authentication on the internet today are name-based or address-based, both of
which are weak.

• Privacy / Confidentiality: Ensuring that no one can read the message except the
intended receiver.

• Integrity: Assuring the receiver that the received message has not been altered in any
way from the original.

• Non-repudiation: A mechanism to prove that the sender really sent this message.

Objectives of Cryptography :-

Modern cryptography concerns itself with the following four objectives:

• Confidentiality: It means that the information can not be understood by anyone for
whom it was unintended.

• Integrity: The information cannot be altered in storage or transit between sender and
intended receiver without the alternation being detected.

• Non-repudiation: The creator / sender of information Cannot deny at a later stage his
or her intentions in the creation or transmission of the information.

• Authentication: The sender and receiver can confirm each other’s identity and the
origin / destination of the information.

Types of Cryptographic Algorithms:-

There are several ways of classifying cryptographic Teorithms. They will be categorized
based on the number of keys that are employed for encryption and decryption, and
further defined by their application and use.

The three types of algorithms are as follows:-

1.Secret key Cryptography (SKC): Uses a single key for both encryption and
decryption.

2.Public Key Cryptography (PKC): Uses one key for encryption and another for
decryption.

3.Hash Functions: Uses a mathematical transformation to irreversibly “encrypt”

information.

1.Symmetric (Private) Key Encryption:-Symmetric encryption is the oldest and best-

known technique. A secret key, which can be a number, a word, or just a string of
random letters, is applied to the text of a message to change the content in a
particular way. This might be as simple as shifting each letter by a number of places in
the alphabet. As long as both sender and recipient know the secret key, then can
encrypt and decrypt all messages that use this key.

2.Asymmetric (Public) Key Encryption :- The most commonly used implementations of

public key cryptography (also known as public-key encryption and asymmetric
encryption) are based on algorithms presented by Rivest-Shamir-Adelman (RSA) for
data security.

Public key cryptography involves a pair of keys known as a public key and a private key
(a public key pair) which are associated with an entity that needs to authenticate it’s
identity electronically or to sign or encrypt data.

Public key cryptography enables the following:

A].Encryption and decryption, which allows two communicating parties to disguise

data that they send to each other. The sender encrypts or scrambles the data before
sending it. The receiver decrypts or unscrambles the data after receiving it. While in
transit, the encrypted data is not understood by an Intruder.

B).Non-repudiation, which prevents:

• The sender of the data from claiming, at a later date, that the data was never sent.

• The data from being altered.

Q .What are firewalls? Explain the working of firewalls and discuss the various types of
firewall ❔

A firewall is a network security device or software that monitors and controls

incoming and outgoing network traffic based on predetermined security rules. It acts
as a barrier between a trusted internal network and untrusted external networks, such
as the Internet, to protect systems from cyber threats.

#How Firewalls Work :-

1*Packet Filtering*: Firewalls examine data packets entering or leaving the network
based on a set of security rules (such as IP addresses, port numbers, and protocols).
Packets matching the rules are allowed; others are blocked.

2*Stateful Inspection: Modern firewalls keep track of the state of active connections
and make decisions based on the context of traffic (e.g., if the request is part of an
ongoing session).

3*Proxying*: A firewall can act as a proxy server, intercepting and filtering traffic
between a user and the destination network.

4*Rule Application:- Administrators define access control rules, which determine

whether traffic is allowed or denied.

5*Logging and Monitoring: Firewalls log traffic activity, enabling system administrators
to monitor network events and detect suspicious behavior.

#Types of Firewalls*

1. Packet-Filtering Firewalls: -

- Operate at the network layer (OSI Layer 3).

- Analyze packets individually without tracking their state.

- Advantages: Simple and efficient.

- Disadvantages: Limited protection as it doesn’t inspect the entire data flow.

2. Stateful Inspection Firewalls:-

- Operate at both the network and transport layers (Layers 3 and 4).
 - Track the state of active connections to make more informed decisions.

- More secure than packet-filtering firewalls.

3. Application-Level Gateways (Proxy Firewalls) :-

- Operate at the application layer (OSI Layer 7).

- Act as intermediaries, inspecting entire messages for malicious content.

- Advantages: High security.

- Disadvantages: Slower due to in-depth inspection.

4. *Next-Generation Firewalls (NGFW)**:

- Incorporate traditional firewall functions with additional features like deep packet
inspection, intrusion detection/prevention, and application awareness.

- Operate at multiple layers for advanced threat protection.

5. Network Address Translation (NAT) Firewalls:

- Mask internal IP addresses by translating them to a public IP.

- Enhance security by hiding the internal network structure.

6. **Cloud Firewalls**:

- Operate in the cloud environment to secure virtual networks.

- Scalable and suited for modern cloud-based applications.

#Benefits of Firewalls :-

- Protect against unauthorized access.

- Prevent malicious traffic from entering the network.

- Enforce organizational security policies.

- Help mitigate risks like data breaches and attacks such as DoS/DDoS.

Firewalls are essential for maintaining network security in both personal and
enterprise environments.

Q.Write a short note on internet service provider ❔

An Internet Service Provider (ISP) is a company or organization that provides

individuals, businesses, and organizations access to the internet. ISPs enable users to
connect to the web for browsing, communication, and other online activities. They
typically offer services such as broadband, wireless connections, hosting, and
sometimes bundled packages like phone and TV services.

#Essential Features to Consider Before Choosing an ISP:-

1. Speed and Bandwidth:-

- Look for download and upload speeds that meet your needs (e.g., streaming,
gaming, remote work).

- Ensure the ISP can handle your required bandwidth without significant slowdowns.

2. Type of Connection:-

- DSL: Budget-friendly but slower compared to other options.

- Cable: Faster than DSL but may slow during peak hours.

- Fiber-optic:- High-speed and reliable but limited in availability.

- Satellite: Ideal for rural areas but slower and more expensive.

3. Reliability and Uptime: - Choose an ISP with a reputation for consistent service and
minimal downtime.

- Look for Service Level Agreements (SLAs) guaranteeing uptime.

4. Coverage Area: - Ensure the ISP offers services in your location.

- Regional ISPs may be better in remote areas.

5. Cost: - Compare pricing plans, including installation fees, equipment costs, and
monthly charges.

- Check for hidden fees or data caps.

6. Customer Support:- Reliable and prompt customer service is crucial for resolving
technical issues quickly.

- Check reviews or ask others about their experience with the ISP.

7. *Security Features:- - Look for built-in features like firewalls, antivirus, or VPN
services to protect your data.

8. Contract Terms:-

- Check if the ISP requires long-term contracts or offers flexible, no-contract plans.
 - Understand penalties for early termination.

9. Additional Services:-

- Many ISPs offer bundled packages with TV, phone, or cloud services.

- Assess if these add-ons provide value for your needs.

10. Scalability(for businesses): - Ensure the ISP can accommodate your future growth
in terms of bandwidth or additional services.

A web browser Is a software application that allows users to access, retrieve, and view
information on the World Wide Web. It interprets and displays content from websites
written in HTML, CSS, JavaScript, and other web technologies. Users interact with web
browsers by entering URLs, clicking on links, or using search engines to navigate the
internet.

#Uses of a Web Browser

1. **Accessing Websites**: Web browsers are used to visit websites and view their
content, such as articles, images, videos, and more.

2. **Online Communication**: Browsers facilitate online communication through

email platforms, video conferencing, and chat applications.

3. **Downloading Files**: They allow users to download files, documents, software,

and media from the internet.

4. **Streaming Content**: Browsers are used to stream videos, music, and other
multimedia content.

5. **Running Web Applications**: Modern browsers support web-based applications

like Google Docs, social media platforms, and cloud-based services.

6. **Secure Transactions**: Web browsers enable online banking, shopping, and other
secure transactions using encryption protocols.

7. **Custom Extensions**: Browsers support extensions and plugins to enhance

functionality, such as ad blockers, password managers, and translation tools.

#Most Widely Used Web Browsers

1. **Google Chrome:-

- Developed by Google.

- Known for its speed, simplicity, and integration with Google services.
 - Supports a wide range of extensions and customization.

- Popular across platforms like Windows, macOS, Android, and iOS.

2. **Mozilla Firefox**

- Developed by Mozilla Foundation.

- Focuses on privacy, security, and open-source principles.

- Known for its customizable interface and privacy-oriented features.

- Supports extensions and tools for developers.

3. **Microsoft Edge**

- Developed by Microsoft as a successor to Internet Explorer.

- Built on the Chromium engine for better performance.

- Integrated with Microsoft services like Office and Windows.

- Includes features like vertical tabs and advanced security settings.

4. **Safari**

- Developed by Apple for macOS and iOS devices.

- Known for its energy efficiency and optimization for Apple hardware.

- Focuses on user privacy with features like Intelligent Tracking Prevention.

- Smooth integration with the Apple ecosystem.

5. **Opera**

- Developed by Opera Software.

- Features built-in ad-blockers, VPN, and messaging apps.

- Known for data-saving and speed-enhancing technologies.

- Popular among users looking for an alternative browser.

6. Brave:-

- Focuses on privacy by blocking ads and trackers.

- Includes built-in cryptocurrency wallet and rewards system for users.

- Based on Chromium, offering speed and compatibility with Chrome extensions.

Q.What are search engines? What should be the features of a good search engines?

A search engine** is a web-based tool that allows users to find information on the
internet by entering keywords or phrases. It scans its database of indexed websites
and returns a list of results ranked based on relevance. Popular search engines
include Google, Bing, Yahoo, and DuckDuckGo.

Search engines rely on algorithms and web crawlers to collect, organize, and rank
information from millions of web pages. Users access search engines to locate
specific content, including websites, images, videos, or documents.

#Features of a Good Search Engine

A good search engine should possess several features to ensure efficiency, user-
friendliness, and reliability. Here are the key features:

1. *Fast and Accurate Search Results: - The engine should provide relevant results
quickly after the query is entered. Accuracy is key to meeting the user’s intent.

2. Comprehensive Indexing: - A good search engine should index a vast range of web
pages to ensure users find diverse information, including lesser-known but valuable
resources.

3. User-Friendly Interface: - The design and functionality should be intuitive, allowing

users of all technical levels to navigate easily.

4. Advanced Search Options: - Features like filters, Boolean operators, date range
selection, and language preferences help refine results for better precision.

5. Personalization:- A search engine should offer personalized results based on the

user’s search history, location, and preferences while maintaining privacy.

6. Support for Multimedia Search: - The engine should allow users to search for
various types of content, such as images, videos, news, and maps, in addition to text.

7. Mobile and Cross-Platform Compatibility: - It should work seamlessly across

devices, including desktops, smartphones, and tablets, ensuring accessibility on the
go.

8. Privacy and Security: - Protecting user data and avoiding the misuse of personal
information are critical. A good search engine should offer encryption and avoid
invasive tracking.

Q.Explain the newsgroups in brief ❔

Ans. Newsgroups

A newsgroup is a place where people discuss a subject of common interest. Whether

you are curious about what’s happening in the news or interested in finding a new
recipe for diner or need help training your dog, there’s a newsgroup out there for you.

Subscribing to Newsgroups

You can find out a list of newsgroups offered by a website by visiting it. If you enjoy a
newsgroup, subscribe to it. The subscription is free. A Web site does not provide you
access to all the newsgroups.

Once you get a list of newsgroups offered by a Web site, you can read the messages
(news). Anyone can participate in a newsgroup and can quickly meet and
communicate with the people who share ideas and interests. You can just read what
others are posting with responding.

To participate in a newsgroup:

A)First you need a newsreader program. Both Internet Explorer and Netscape
Navigator have built-in newsreader program.

B)Determine which newsgroups interest you.

C)Subscribe to the interested newsgroup.

The example below shows you the path to participate in the newsgroups offered by
Yahoo Website:

1.Enter the URL of the Yahoo groups, ie http://groups.yahoo.com.

2.The yahoo group page appears.

3.Type a topic in the Search box and then click the Search button. For example, type
Computer in the Search box and then click the Search button. Accordingly the search
results page will be displayed.

4.On the Search Result page select the group, which you want to join.

5.Select an article (message) to read it. Read the message and if you want to post
(send) a follow-up message, click on the hyperlink – Post Message at the end.

Types of Newsgroups

There are two types of newsgroups on Usenet:

• Moderated Newsgroups: In a moderated newsgroup, each message is examined by a
human moderator before passed on to the workgroup.

• Unmoderated Newsgroups: In an unmoderated newsgroup, all messages are

automatically posted and are distributed to all groups by Usenet servers.

Working of Usenet Newsgroups:-

Working of Usenet Newsgroup is based on client-server model. Therefore, there are

two main components of Usenet – News Server and News Reader (Client). The Articles
posted in newsgroups are distributed over Internet by News Servers.

Hierarchies of Newsgroups:-

Usenet newsgroups are divided into hierarchies. The number of newsgroups on the
Usenet is so large that they are arranged in hierarchy to make them manageable. Like
regular domain names, they also have dots separating the different parts of their
hierarchy. One example of this is the newsgroup ric.arts.books.

For example,

• Comp is for discussion on computer-related topics.

• Sci is for discussion on scientific topics.

• Soc is for discussion on social topics.

Purpose of Usenet Newsgroup :-

The purpose of a newsgroup is to create an avenue for the exchange of information and
ideas. It provides online discussions on a small business with opportunities for
networking, learning more about the competition and industry, sales possibility and
marketing.

Q.Describe the HTTP protocol and its features with an example ❔

HTTP

HTTP refers to Hypertext Transfer Protocol. It is a standard communication protocol. It

is the set of rules that governs the transfer of hypertext between two or more
computers.

Computers on the World Wide Web use the Hyper Text Transfer Protocol to talk with
each other. The HTTP provides a set of instructions for accurate information exchange.

Features of HTTP
Following are the features of HTTP:

1. Request Response Mechanism

2. Connectionless Protocol
3. Stateless Protocol
4. Resource Identification

1. Request-Response Mechanism

HTTP is based on the client / server principle. It allows the client to establish a
connection to the server and make a request. A web browser is an HTTP client because
it sends requests to a web server, which then sends responses back to the client
followed by the contents of the HTML page (the requested resource). Any HTTP server
responds to the browser on request. The HTTP request / response transaction involves
the following major steps:

• Client establishes a connection

• Client sends the request

• Server responds

• Connection is closed

HTTP transactions are always initiated by the client and server never generates a
response without being asked for it by a client. HTTP is a simple protocol, but it can
carry quite complex data. HTTP is the protocol to exchange or transfer hypertext.

2 Connectionless Protocol:-Here connectionless means that the connection is closed

as soon as the client’s requirement is over. While working with this protocol, the client
sets a connection, sends request to the server, receives a response and then closes
the connection. So each request requires opening a new connection. The connection
is closed after a single request/response.

2.Stateless Protocol:-A stateless protocol does not require the HTTP server to retain
any information or status about prior transactions. Subsequent request / response
pairs are completely independent of any past or previous client requests.

Q.Define Protocol. Explain protocols of communication in detail ❔

Protocols of Communication
Protocols of communication are the formal descriptions of digital message formats
and rules. They are required to exchange messages in or between computing systems
and are required in telecommunications.

Popular communication protocols include

1. Address Resolution Protocol (ARP)

2. Simple Mail Transfer Protocol (SMTP)
3. Reverse Address Resolution Protocol (RARP)
4. Multi-Purpose Internet Mail Extension (MIME)
5. Internet Message Access Protocol (IMAP)
6. Post Office Protocol (POP)
7. Internet Control message Protocol (ICMP)

1.Address Resolution Protocol (ARP):- One of the basic communication protocols is

the ARP. ARP resolves the IOP addresses used by various networking devices into
network usable format used by LANS. ARP serves two basic services to the clients; it
obtains the media control address for the requesting device and recording of Media
Access Control (MAC) address in a table called the ARP cache for future use.

2.Simple Mail Transfer Protocol (SMTP):-The Simple Mail Transfer Protocol (SMTP) is
the standard e-mail protocol of the Internet. SMTP is the standard protocol for sending
emails across Internet.

It is a set of communication guidelines that allow software to transmit email over the
Internet. Most email software is designed to use SMTP for communication purposes
when sending email and it only works for outgoing messages

3.Multi-Purpose Internet Mail Extension (MIME):-MIME stands for Multi-purpose

Internet Mail Extension. MIME is a supplementary protocol to SMTP that allows non-
ASCII data such as binary files, sound files, video files, etc., to be included in the
message (mail) through SMTP send it over the internet.

4.Internet Message Access Protocol (IMAP):-Internet Message Access Protocol (IMAP)

is a standard protocol for accessing e-mail from your local server. IMAP is a client /
server protocol in which e-mail is received and held by Internet server. IMAP performs
the same basic functions as POP but can also perform additional features.

5.Post Office Protocol (POP):-Post Office Protocol (POP) is responsible for obtaining e-
mail from the mail server. To send to or collect.
Q.Write a note on intranet security design ❔

Ans, Intranet Security Design

The intranet serves as a powerful tool for communication within an organization. It

supports communication channels, such as information from the management team
concerning strategic aspects of their organization or collaboration amongst project
teams and departments.

Following are some key considerations for designing an intranet with robust security:

1. Network Segmentation
2. Access Control
3. Firewalls and Perimeter Security
4. Strong Authentication
5. Secure Remote Access
6. Encryption
7. Regular Updates and Patching
8. Employce Awareness and Training
9. Monitoring and Logging

1.Network Segmentation:-Network segmentation involves dividing the intranet into

separate segments or subnets based on data sensitivity and security requirements. It
helps contain potential security breaches and limits lateral movement of threats
within the network.

2.Access Control:-Access control means implementing strong access control

mechanisms in order to ensure that only authorized individuals can access sensitive
resources on the intranet.

This includes user authentication, authorization based on user roles and privileges,
and periodic access reviews.

3.Firewalls and Perimeter Security:-Deploying firewalls and other perimeter security

measures is essential to control inbound and outbound network traffic. By configuring
firewalls to allow only authorized traffic and blocking unauthorized access attempts,
organizations can minimize the risk of external threats.

4.Strong Authentication:-Using strong passwords and implementing multi-factor

authentication (MFA) for accessing critical systems and resources adds an extra layer
of security. MFA requires users to provide additional proof of identity.