Web and internet technology notes for BCA students

its help for student in their examination in BCA course

1. TCP
TCP is a connection-oriented protocol, which means that it first establishes the
connection between the sender and receiver in the form of a handshake. After both the
connections are verified, it begins transmitting packets. It makes the transmission
process error-free and ensures the delivery of data. It is an important part of the
communication protocols used to interconnect network devices on the internet. The
whole internet system relies on this network.
TCP is one of the most common protocols that ensure end-to-end delivery. It
guarantees the security and integrity of the data being transmitted. It always
establishes a secure connection between the sender and receiver. The transmitter is
the server, and the receiver is known as the client. We can also say that the data
transmission occurs between the server and client. Hence, TCP is used in most of the
high-level protocols, such as FTP (File Transfer Protocol), HTTP (Hyper Text Transfer
Protocol), and SMTP (Simple Mai Transfer Protocol).

Write down different services of TCP.
Following are some of the services offered by the Transmission Control Protocol (TCP) to the
processes at the application layer:

Stream Delivery Service.
Sending and Receiving Buffers.
Bytes and Segments.
Full Duplex Service
Connection Oriented Service.
Reliable Service.


How TCP does compute checksum?
The Transmission Control Protocol (TCP) checksum is a method used to detect errors in TCP
packets. The checksum is calculated by taking the binary value of all the fields in the TCP
header and the data, treating them as a large integer, and then performing a bit-wise ones
complement on that integer.

To calculate the TCP checksum, the following steps are performed −

The checksum field in the TCP header is set to zero.
The binary values of the source and destination IP addresses, the reserved field, the protocol
field (set to 6 for TCP), the TCP length, and the TCP data are concatenated.
The resulting binary value is treated as a large integer and a bit-wise ones complement is
taken.
The resulting value is then converted to 16-bit binary and placed in the checksum field of the
TCP header.

2. Write TCP connections close process with a help of diagram.

TCP termination process with the help of six steps that includes the sent requests and
the waiting states. The steps are as follows:
Step 1: FIN
FIN refers to the termination request sent by the client to the server. The first FIN
termination request is sent by the client to the server. It depicts the start of the
termination process between the client and server.
Step 2: FIN_ACK_WAIT
The client waits for the ACK of the FIN termination request from the server. It is
a waiting state for the client.
Step 3: ACK
The server sends the ACK (Acknowledgement) segment when it receives the FIN
termination request. It depicts that the server is ready to close and terminate the
connection.
Step 4: FIN _WAIT_2
The client waits for the FIN segment from the server. It is a type of approved signal
sent by the server that shows that the server is ready to terminate the connection.
Step 5: FIN
The FIN segment is now sent by the server to the client. It is a confirmation signal that
the server sends to the client. It depicts the successful approval for the termination.
Step 6: ACK
The client now sends the ACK (Acknowledgement) segment to the server that it has
received the FIN signal, which is a signal from the server to terminate the connection.
As soon as the server receives the ACK segment, it terminates the connection.

3. Difference between OSI Model and TCP/IP Model
Parameters OSI Model TCP/IP Model
Full Form
OSI stands for Open Systems
Interconnection.
TCP/IP stands for Transmission
Control Protocol/Internet Protocol.
Layers It has 7 layers. It has 4 layers.
Usage It is low in usage. It is mostly used.
Approach It is vertically approached. It is horizontally approached.
Delivery
Delivery of the package is
guaranteed in OSI Model.
Delivery of the package is not
guaranteed in TCP/IP Model.
Replacement
Replacement of tools and changes
can easily be done in this model.
Replacing the tools is not easy as it is
in OSI Model.
Reliability It is less reliable than TCP/IP Model. It is more reliable than OSI Model.





Similarities Between TCP/IP Model and OSI Model
Similarities TCP/IP and OSI Model
Model Both TCP/IP are logical models.
Structure



Both are arranged layered wise which is also called an
architectural model. These models have a stack of protocols
it means the protocol is arranged in every layer. Both models
have some set of protocols.
Networking Both TCP/IP defines standards for networking.
Framework
Both TCP/IPs provide a framework for creating and
implementing networking standards and devices.
Communication process
Both TCP/IPs simplify and divide the network
communication process into making their layers.

4. Similarities TCP/IP and OSI Model
Similar components
In Both TCP/IP models manufacturer allows making sets of
devices and network components that can co-exist and work
with the devices and components that are made by the other
manufacturers.
functionality
In both TCP/IP models, a single layer defines a particular
functionality and set standards for that functionality only.
Troubleshooting
Both the TCP/IP models simplify their troubleshooting
process by dividing the layer’s complex functions into simpler
components of the layer.
Ethernet standards
Instead of defining the already defined standards and
protocols in both the TCP/IP models. For example, the
Ethernet standards were already defined by IEEE before
proceeding to create these models. So instead of defining
them again in both the models of IEEE Ethernet standards
What do you mean by “endpoints of TCP connections”?

Endpoints of TCP connections are identified by host IP and port number.

A TCP endpoint is a combination of an IP address and a port number that identifies a specific
process or service running on a computer or other network device. It is used to establish and
manage an end-to-end connection between two applications, typically over the Internet.

Explain the connection establishment of TCP.

5. TCP Connection (A 3-way handshake)
The diagram of a successful TCP connection showing the three handshakes is shown below:

The three handshakes are discussed
in the below steps:
Step 1: SYN
SYN is a segment sent by the client to
the server. It acts as a connection
request between the client and
server. It informs the server that the
client wants to establish a
connection. Synchronizing sequence
numbers also helps synchronize
sequence numbers sent between any
two devices, where the same SYN
segment asks for the sequence
number with the connection request.
Step 2: SYN-ACK
It is an SYN-ACK segment or an SYN + ACK segment sent by the server. The ACK segment
informs the client that the server has received the connection request and it is ready to build
the connection. The SYN segment informs the sequence number with which the server is ready
to start with the segments.
Step 3: ACK
ACK (Acknowledgment) is the last step before establishing a successful TCP connection
between the client and server. The ACK segment is sent by the client as the response of the
received ACK and SN from the server. It results in the establishment of a reliable data
connection.
After these three steps, the client and server are ready for the data communication process.
TCP connection and termination are full-duplex, which means that the data can travel in both
the directions simultaneously.
What is passive and active opens in TCP.
Active and Passive OPENs
TCP/IP is based on the client/server model of operation, and TCP connection setup is based
on the existence of these roles as well. The client and server each prepare for the connection
by performing an OPEN operation. However, there are two different kinds of OPEN:
o Active OPEN: A client process using TCP takes the “active role” and initiates the
connection by actually sending a TCP message to start the connection (a SYN message).
o Passive OPEN: A server process designed to use TCP, however, takes a more “laid-back”
approach. It performs a passive OPEN by contacting TCP and saying “I am here, and I
am waiting for clients that may wish to talk to me to send me a message on the
following port number”. The OPEN is called passive because aside from indicating that
the process is listening, the server process does nothing.
A passive OPEN can in fact specify that the server is waiting for an active OPEN from a specific
client, though not all TCP/IP APIs support this capability. More commonly, a server process is
willing to accept connections from all comers. Such a passive OPEN is said to be unspecified.

6. Active FTP Passive FTP
In active FTP, client establishes the
command channel and the server establishes
the data channel.
In passive FTP, both the command
channel and the data channel are
established by the client.
Active FTP provides security to the FTP
server.
Passive FTP does not provide security to
the FTP server.
Active FTP may cause problems because of
firewalls.
Passive FTP does not have connection
issues from firewalls.
Active mode is not used as a default mode of
a browser.
Passive mode is used as a default mode of
a browser.
FTP client acknowledges on data channel. FTP server acknowledges on data channel.
Client sends random port number to the
server.
Client sends PASV command to the server.
In Active FTP, the data connection is made
and the file transfers are then done through
client and server ports.

In passive FTP, the client still have to
initiates the command channel (control
connection) to the server.
Write two differences between TCP and UDP.


TCP UDP
Full form It stands for Transmission
Control Protocol.
It stands for User Datagram
Protocol.
Type of connection It is a connection -oriented
protocol, which means that the
connection needs to be
established before the data is
transmitted over the network.
It is a connectionless protocol,
which means that it sends the
data without checking whether
the system is ready to receive
or not.
Reliable TCP is a reliable protocol as it
provides assurance for the
delivery of data packets.
UDP is an unreliable protocol
as it does not take the
guarantee for the delivery of
packets.

7. Speed TCP is slower than UDP as it
performs error checking, flow
control, and provides assurance
for the delivery of
UDP is faster than TCP as it
does not guarantee the delivery
of data packets.
Header size The size of TCP is 20 bytes. The size of the UDP is 8 bytes.
Acknowledgment TCP uses the three -way-
handshake concept. In this
concept, if the sender receives
the ACK, then the sender will
send the data. TCP also has the
ability to resend the lost data.
UDP does not wait for any
acknowledgment; it just sends
the data.
Flow control
mechanism
It follows the flow control
mechanism in which too many
packets cannot be sent to the
receiver at the same time.
This protocol follows no such
mechanism.
Error checking TCP performs error checking by
using a checksum. When the
data is corrected, then the data
is retransmitted to the receiver.
It does not perform any error
checking, and also does not
resend the lost data packets.
Applications This protocol is mainly used
where a secure and reliable
communication process is
required, like military services,
web browsing, and e-mail.
This protocol is used where
fast communication is required
and does not care about the
reliability like VoIP, game
streaming, video and music
streaming, etc.



Telnet
Telnet is a standard TCP/IP protocol for providing virtual terminal services standardized by
ISO. In this protocol, the client-server first sets up a connection link with the remote server
and then keystrokes from the user’s keyboard are transferred directly to the remote computer,
which looks like the keystrokes were passed from the keyboard connected to the machine. The
result is also carried back to the user from the remote machine. The process is considered to
be transparent to the users because it seems like the user is directly attached to the remote
machine. The remote machine is identified by Telnet client software through defining either of
its IP address or domain name.

8. BASIS FOR
COMPARISON
TELNET FTP
Basic It allows a user to log in to the
remote server.
It allows a user to transfer a file to the
remote machine.
Functions on Port
number
23 21 and 20
Security May have some security
concerns.
More secure than Telnet.
Remote login Is required to access the system
resources.
Not necessarily needed.

How does Telnet Works?
 It makes available users by an interactive and bidirectional text-oriented
message system exploit an effective terminal connection which is much more
than 8 byte.
 User data is sprinkled in the band long with telnet control information above the
TCP. It helps to achieve some functions in a remote manner.
 The user joins the server beside using the TCP protocol, so that means like the
other side connection is also established using the telnet hostname.
Following are the uses of telnet.
 PuTTY and plink: CLI, which is free and provides SSH,rlogin, Telnet, and raw
TCP client for Unix, Linux, and windows.
 Line Mode Browser
 Van Dyke Softwares SecureCRT
 Georgia SoftWorks GSW ConnectBot.
 ZOC Terminal
 SyncTERM BBS terminal: A program that supports SSHv2, RLogin, Telnet,
Serial, *nix, Windows and Mac OS X platforms and other BBS terminal
emulations

9.  NetRunner BBS telnet client: used mainly for ANSI-BBS. SDL2 oriented
emulation engine is employed to offer largely accurate and transparent
emulation.
 NCSA Telnet
 TeraTerm
 Rtelnet: It is a SOCKS version of telnet, given the comparable functionality of
telnet for its hosts falling behind a firewall.
 Terminal emulator RUMBA
 Inetutils: It over again comprises a telnet client and server.
 exe: another CLI utility included in a default installation of Microsoft Windows
OS.
Advantages of Telnet
1. It provides remote access to someone’s computer system.
2. Telnet allows the user for more access with fewer problems in data
transmission.
3. Telnet saves a lot of time.
4. The oldest system can be connected to a newer system with telnet having
different operating systems.
Disadvantages of Telnet
1. As it is somehow complex, it becomes difficult to beginners in understanding.
2. Data is sent here in form of plain text, that’s why it is not so secured.
3. Some capabilities are disabled because of not proper interlinking of the
remote and local devices.
What are telnet clients?
The Telnet client enables a TCP/IP user to sign on and use applications on a remote system by
using a Telnet server application. Telnet allows you to log on to the remote computer and use it
as if you were connected directly to it.

10. UNIT VIII. Internet Security: Overview of Internet Security threats,
Firewalls, Malware and its type, Introduction to AAA.
Explain in brief different Cyber Security Threats
Cyber security professionals should have an in-depth understanding of the
following types of cyber security threats.
1. Malware
Malware is malicious software such as spyware, ransomware, viruses and
worms. Malware is activated when a user clicks on a malicious link or
attachment, which leads to installing dangerous software. Cisco reports that
malware, once activated, can:
Block access to key network components (ransomware)
Install additional harmful software
Covertly obtain information by transmitting data from the hard drive
(spyware)
Disrupt individual parts, making the system inoperable
2. Emotet
The Cybersecurity and Infrastructure Security Agency (CISA) describes
Emotet as “an advanced, modular banking Trojan that primarily functions
as a downloader or dropper of other banking Trojans. Emotet continues to
be among the most costly and destructive malware.”

3. Denial of Service
A denial of service (DoS) is a type of cyber attack that floods a computer or
network so it can’t respond to requests. A distributed DoS (DDoS) does the
same thing, but the attack originates from a computer network. Cyber
attackers often use a flood attack to disrupt the “handshake” process and
carry out a DoS. Several other techniques may be used, and some cyber
attackers use the time that a network is disabled to launch other attacks. A
botnet is a type of DDoS in which millions of systems can be infected with
malware and controlled by a hacker, according to Jeff Melnick of Netwrix, an
information technology security software company. Botnets, sometimes
called zombie systems, target and overwhelm a target’s processing
capabilities. Botnets are in different geographic locations and hard to trace.

11. 4. Man in the Middle
A man-in-the-middle (MITM) attack occurs when hackers insert themselves
into a two-party transaction. After interrupting the traffic, they can filter and
steal data, according to Cisco. MITM attacks often occur when a visitor uses
an unsecured public Wi-Fi network. Attackers insert themselves between
the visitor and the network, and then use malware to install software and
use data maliciously.

5. Phishing
Phishing attacks use fake communication, such as an email, to trick the
receiver into opening it and carrying out the instructions inside, such as
providing a credit card number. “The goal is to steal sensitive data like credit
card and login information or to install malware on the victim’s machine,”
Cisco reports.

6. SQL Injection
A Structured Query Language (SQL) injection is a type of cyber attack that
results from inserting malicious code into a server that uses SQL. When
infected, the server releases information. Submitting the malicious code can
be as simple as entering it into a vulnerable website search box.

7. Password Attacks
With the right password, a cyber attacker has access to a wealth of
information. Social engineering is a type of password attack that Data
Insider defines as “a strategy cyber attackers use that relies heavily on
human interaction and often involves tricking people into breaking standard
security practices.” Other types of password attacks include accessing a
password database or outright guessing

12. Why Do Cybercriminals Use Malware?
Cybercriminals use malware, which includes all forms of malicious software
including viruses, for a variety of purposes.
Using deception to induce a victim to provide personal information for
identity theft
Theft of customer credit card information or other financial information
Taking over several computers and using them to launch denial-of-service
attacks against other networks
Using infected computers to mine for cryptocurrencies like bitcoin.

Discuss different types of malware.
Viruses – A Virus is a malicious executable code attached to another
executable file. The virus spreads when an infected file is passed from
system to system. Viruses can be harmless or they can modify or delete
data. Opening a file can trigger a virus. Once a program virus is active, it
will infect other programs on the computer.
Worms – Worms replicate themselves on the system, attaching themselves to
different files and looking for pathways between computers, such as
computer network that shares common file storage areas. Worms usually
slow down networks. A virus needs a host program to run but worms can
run by themselves. After a worm affects a host, it is able to spread very
quickly over the network.
Trojan horse – A Trojan horse is malware that carries out malicious
operations under the appearance of a desired operation such as playing an
online game. A Trojan horse varies from a virus because the Trojan binds
itself to non-executable files, such as image files, and audio files.
Ransomware – Ransomware grasps a computer system or the data it
contains until the victim makes a payment. Ransomware encrypts data in
the computer with a key that is unknown to the user. The user has to pay a
ransom (price) to the criminals to retrieve data. Once the amount is paid the
victim can resume using his/her system
Adware – It displays unwanted ads and pop-ups on the computer. It comes
along with software downloads and packages. It generates revenue for the
software distributer by displaying ads.

13. Spyware – Its purpose is to steal private information from a computer
system for a third party. Spyware collects information and sends it to the
hacker.
Logic Bombs – A logic bomb is a malicious program that uses a trigger to
activate the malicious code. The logic bomb remains non-functioning until
that trigger event happens. Once triggered, a logic bomb implements a
malicious code that causes harm to a computer. Cybersecurity specialists
recently discovered logic bombs that attack and destroy the hardware
components in a workstation or server including the cooling fans, hard
drives, and power supplies. The logic bomb overdrives these devices until
they overheat or fail.
Rootkits – A rootkit modifies the OS to make a backdoor. Attackers then use
the backdoor to access the computer distantly. Most rootkits take advantage
of software vulnerabilities to modify system files.
Backdoors – A backdoor bypasses the usual authentication used to access a
system. The purpose of the backdoor is to grant cyber criminals future
access to the system even if the organization fixes the original vulnerability
used to attack the system.
Keyloggers – Keylogger records everything the user types on his/her
computer system to obtain passwords and other sensitive information and
send them to the source of the keylogging program

14. WEB AND INTERNET TECHNOLOGY
What is an Internet?
A complete network of globally linked computers, the Internet also enables the users
to transfer information and communication. This makes use of the TCP/IP protocol
suite while communicating. Available in both wired and wireless mode, the internet
also includes a wide range of networks such as private, public, government,
organisation, etc. It supports multiple users and allows the transfer of a massive
amount of data.
What is an Intranet?
A part of the network, but controlled and used by a private organisation, Intranet has
restrictions and can support only fewer users. Hence, only limited data can be shared
over it. Intranet is usually operated on a client/server platform. This enables the
organisations to share files, data, organise information, manage and share calendars,
files, etc.
What is the Difference between Internet and
Intranet?
A wide network of computers available for all is the internet, while the intranet is a
network of computers designed for a certain group of users. The internet is a public
network, while an intranet is a private network. Learn more about what is the
difference between internet and intranet, from the table below
INTERNET INTRANET
Simultaneously link computers on different
network / global network
Owned by local or private organisations / companies
Support multiple users Users are limited
Unsafe, not protected Protected and secured

15. What is Internet Connection?
A user can connect to the Internet either by dialing into an ISP's computer or by
directly connecting to the ISP. A dial-up connection is the one you initiate by dialing
into a modem over a telephone link whereas a direct connection is a continuous
connection to an ISP through a dedicated phone line.
The various types of Internet connections are:
o Dial-up connection
o ISDN
o Leased Line or TI/T3 connections
o DSL
o Cable TV Internet connections
o Satellite Internet Connections
o Wireless Internet Connections
Client and Server model
o A client and server networking model is a model in which computers such as servers
provide the network services to the other computers such as clients to perform a user
based tasks. This model is known as client-server networking model.
o The application programs using the client-server model should follow the given
below strategies:
Client
It’s a public network with more traffic A private network and traffic is less
Can transfer unlimited data Can transfer only limited data
Can be widely accessed and used Company or organisation employees or admin with
access to login details can only use this
More data or information can be accessed or
availed
Data or information accessible over intranet will be
limited and specific to the company records or details

16. A client is a program that runs on the local machine requesting service from the
server. A client program is a finite program means that the service started by the user
and terminates when the service is completed.
Server
A server is a program that runs on the remote machine providing services to the
clients. When the client requests for a service, then the server opens the door for the
incoming requests, but it never initiates the service.
A server program is an infinite program means that when it starts, it runs infinitely
unless the problem arises. The server waits for the incoming requests from the
clients. When the request arrives at the server, then it responds to the request.
Advantages of Client-server networks:
o Centralized: Centralized back-up is possible in client-server networks, i.e., all the data
is stored in a server.
o Security: These networks are more secure as all the shared resources are centrally
administered.
o Performance: The use of the dedicated server increases the speed of sharing
resources. This increases the performance of the overall system.
o Scalability: We can increase the number of clients and servers separately, i.e., the
new element can be added, or we can add a new node in a network at any time.
What is TCP?
Transmission Control Protocol (TCP) is a communications standard that enables
application programs and computing devices to exchange messages over a network. It
is designed to send packets across the internet and ensure the successful delivery of
data and messages over networks.
TCP is one of the basic standards that define the rules of the internet and is included
within the standards defined by the Internet Engineering Task Force (IETF). It is one of
the most commonly used protocols within digital network communications and ensures
end-to-end data delivery.
TCP organizes data so that it can be transmitted between a server and a client. It
guarantees the integrity of the data being communicated over a network. Before it
transmits data, TCP establishes a connection between a source and its destination,
which it ensures remains live until communication begins. It then breaks large amounts
of data into smaller packets, while ensuring data integrity is in place throughout the
process.

17. What is IP?
The Internet Protocol (IP) is the method for sending data from one device to another
across the internet. Every device has an IP address that uniquely identifies it and
enables it to communicate with and exchange data with other devices connected to the
internet. Today, it’s considered the standard for fast and secure communication directly
between mobile devices.
IP is responsible for defining how applications and devices exchange packets of data
with each other. It is the principal communications protocol responsible for the formats
and rules for exchanging data and messages between computers on a single network or
several internet-connected networks. It does this through the Internet Protocol Suite
(TCP/IP), a group of communications protocols that are split into four abstraction layers.
IP is the main protocol within the internet layer of the TCP/IP. Its main purpose is to
deliver data packets between the source application or device and the destination using
methods and structures that place tags, such as address information, within data
packets.
The 4 Layers of the TCP/IP Model
The TCP/IP model defines how devices should transmit data between them and enables
communication over networks and large distances. The model represents how data is
exchanged and organized over networks. It is split into four layers, which set the
standards for data exchange and represent how data is handled and packaged when
being delivered between applications, devices, and servers.
The four layers of the TCP/IP model are as follows:
1. Datalink layer: The datalink layer defines how data should be sent, handles the
physical act of sending and receiving data, and is responsible for transmitting
data between applications or devices on a network. This includes defining how
data should be signaled by hardware and other transmission devices on a
network, such as a computer’s device driver, an Ethernet cable, a network
interface card (NIC), or a wireless network. It is also referred to as the link layer,
network access layer, network interface layer, or physical layer and is the
combination of the physical and data link layers of the Open Systems
Interconnection (OSI) model, which standardizes communications functions on
computing and telecommunications systems.
2. Internet layer: The internet layer is responsible for sending packets from a
network and controlling their movement across a network to ensure they reach
their destination. It provides the functions and procedures for transferring data
sequences between applications and devices across networks.
3. Transport layer: The transport layer is responsible for providing a solid and
reliable data connection between the original application or device and its
intended destination. This is the level where data is divided into packets and
numbered to create a sequence. The transport layer then determines how much
data must be sent, where it should be sent to, and at what rate. It ensures that
data packets are sent without errors and in sequence and obtains the
acknowledgment that the destination device has received the data packets.

18. 4. Application layer: The application layer refers to programs that need TCP/IP to
help them communicate with each other. This is the level that users typically
interact with, such as email systems and messaging platforms. It combines the
session, presentation, and application layers of the OSI model.

Introduction to TELNET
TELNET stands for Teletype Network. It is a type of protocol that enables one
computer to connect to the local computer. It is used as a standard TCP/IP
protocol for virtual terminal service which is provided by ISO. The computer which
starts the connection is known as the local computer.
The computer which is being connected to i.e. which accepts the connection known
as the remote computer.
During telnet operation, whatever is being performed on the remote computer will be
displayed by the local computer. Telnet operates on a client/server principle. The
local computer uses a telnet client program and the remote computers use a telnet
server program
Daemon Meaning
A daemon is a program that runs continuously in the background of a multitasking
operating system, meaning that daemons are not under the user’s direct control. A
specific action or event activates daemons. Most daemon file names end with the
letter d.
While scripts like init or systemd start most daemons when a system boots up, some
start manually. Examples of manually triggered daemons are:
 mysqld: Database server
 httpd:Web server
Daemon vs Process
As explained above, a daemon is a non-interactive program. It runs all the time, and
it’s not connected to the terminal. Even when you close the terminal, the operating
system will not stop the daemon as it will run in the background.
On the other hand, a process will stop when the terminal closes because it is
an executing program instance.
Managing the Telnet client
The Telnet client enables a TCP/IP user to sign on and use applications on a remote
system by using a Telnet server application. Telnet allows you to log on to the
remote computer and use it as if you were connected directly to it. You can run
programs, change configurations, or do just almost anything else you can do.

19. Telnet makes your computer act like a mainframe computer's workstation. In other
words, when using Telnet, your computer (the client) pretends to be, or emulates, a
terminal directly attached to the remote computer (the Telnet server).
Terminal Emulator
Terminal Emulator is any hardware and/or software that allows a PC to operate as a terminal
and connect to a back-end mainframe or terminal server. Terminal emulators can be
designed to emulate specific terminal modes such as ANSI, VT52, VT100, VT220, TN3270,
or TN5250.
Internet Relay Chat (IRC)

Internet Relay Chat (IRC) is an Internet application that was developed by Jakko
Oikarinen in Finland. Chat is the most convenient immediate way to communicate
with others via Internet. There are a number of topics called “channels” through
which you can chat with many people all over the world. After joining channel, you
can see what other people on this channel type on their keyboards. In that situation,
everyone on this channel can see whatever you type on your keyboard. You can also
hold individual conversations with someone. Channels get live on different servers
around the world. Some servers have only a few channels, while others have many
of them.

Introduction to Internet, WWW and Web
Browsers
Internet is a global communication system that links together thousands of individual
networks. It allows exchange of information between two or more computers on a network.
Thus internet helps in transfer of messages through mail, chat, video & audio conference, etc.
It has become mandatory for day-to-day activities: bills payment, online shopping and
surfing, tutoring, working, communicating with peers, etc.
In this topic, we are going to discuss in detail about concepts like basics of computer
networks, Local Area Network (LAN), Wide Area Network (WAN), concept of internet,
basics of internet architecture, services on internet, World Wide Web and websites,
communication on internet, internet services, preparing computer for internet access, ISPs
and examples (Broadband/Dialup/Wi-Fi), internet access techniques, web browsing software,
popular web browsing software, configuring web browser, search engines, popular search
engines/search for content, accessing web browser, using favorites folder, downloading web
pages and printing web pages.
What is a Browser?
A browser is a software program that is used to explore, retrieve, and display the
information available on the World Wide Web. This information may be in the form
of pictures, web pages, videos, and other files that all are connected via hyperlinks

20. and categorized with the help of URLs (Uniform Resource Identifiers). For example,
you are viewing this page by using a browser.
A browser is a client program as it runs on a user computer or mobile device and
contacts the webserver for the information requested by the user. The web server
sends the data back to the browser that displays the results on internet supported
devices. On behalf of the users, the browser sends requests to web servers all over
the internet by using HTTP (Hypertext Transfer Protocol). A browser requires a
smartphone, computer, or tablet and internet to work.
History of Web Browser
o The WorldWideWeb was the first web browser. It was created by W3C Director Tim
Berners-Lee in 1990. Later, it was renamed Nexus to avoid confusion caused by the
actual World Wide Web.
o The Lynx browser was a text-based browser, which was invented in 1992. It was not
able to display the graphical content.
o Although, the first graphical user interface browser was NCSA Mosaic. It was the first
most popular browser in the world, which was introduced in 1993.
o In 1994, there were some improvements occurred in Mosaic and came to Netscape
Navigator.
o In 1995, Microsoft introduced the Internet Explorer It was the first web browser
developed by Microsoft.
o A research project started on Opera in 1994. Later, it was publicly introduced in 1996.
o Apple's Safari browser was introduced in 2003. It was specifically released for
Macintosh computers.
o In 2004, Mozilla introduced Firefox as Netscape Navigator.
o In 2007, a browser Mobile Safari was released as Apple mobile web browser.
o The popular browser Google Chrome was launched in 2008.
o The fast-growing mobile-based browser Opera Mini was released in 2011.
o The Microsoft Edge browser was launched in 2015.
Features of Web Browser
Most Web browsers offer common features such as:
1. Refresh button: Refresh button allows the website to reload the contents of the web
pages. Most of the web browsers store local copies of visited pages to enhance the

21. performance by using a caching mechanism. Sometimes, it stops you from seeing the
updated information; in this case, by clicking on the refresh button, you can see the
updated information.
2. Stop button: It is used to cancel the communication of the web browser with the
server and stops loading the page content. For example, if any malicious site enters
the browser accidentally, it helps to save from it by clicking on the stop button.
3. Home button: It provides users the option to bring up the predefined home page of
the website.
4. Web address bar: It allows the users to enter a web address in the address bar and
visit the website.
5. Tabbed browsing: It provides users the option to open multiple websites on a single
window. It helps users to read different websites at the same time. For example, when
you search for anything on the browser, it provides you a list of search results for your
query. You can open all the results by right-clicking on each link, staying on the same
page.
6. Bookmarks: It allows the users to select particular website to save it for the later
retrieval of information, which is predefined by the users.
What is the URL (Uniform Resource Locator)?
A uniform resource locator is the address of a resource on the internet or
the World Wide Web. It is also known as a web address or uniform resource identifier
(URI). For example, https: www.javatpoint.com, which is the URL or web address for
the javatpoint website. A URL represents the address of a resource, including the
protocol used to access it
URLs and HTTP
Web clients are browsers, like IE. Browsers send requests to web servers (like
Apache). A typical request is to download a web page. A browser usually makes
this request when the user clicks a link in a web page.
The requested web page is identified by its Uniform Resource Locator (URL).
The format of a URL is:
protocol://server/page
For example:
http://www.unc.edu/home.html
In this example www.unc.edu is the server's domain name address.

22. The page is an HTML document.
A protocol is a conversational pattern. It's like a script in a play. It specifies the
type and format of a client's request as well as the type and format of the server's
response.
In the example above the protocol is http, which stands for Hyper Text Transfer
Protocol.
HTTP
HTTP is a simple, stateless protocol. The browser sends a request to download
(GET or POST), update (UPDATE), or delete (DELETE) a web page. In the case of a
download, the server responds by sending an HTML document back to the
browser. Most servers disable the UPDATE and DELETE commands.
Websites Publishing

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Website publishing is the process of uploading content on the internet. It includes:
 uploading files
 updating web pages
 posting blogs
Website is published by uploading files on the remote server which is provided by the hosting
company.
Prerequisites for Website Publishing
In order to publish your site, you need the following things:
 Web development software
 Internet Connection
 Web Server
Web development software
It is used for building web pages for your web site. Dreamweaver and WordPress are
example of web development softwares.
Internet Connection
Internet connection is required to connect to a remotely located web server.
Web Server
Web server is the actual location where your website resides on. A web server may host
single or multiple sites depending on what hosting service you have paid for.

23. websites Hosting

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Overview
Web hosting is a service of providing online space for storage of web pages. These web
pages are made available via World Wide Web. The companies which offer website hosting
are known as Web hosts.
The servers on which web site is hosted remain switched on 24 x7. These servers are run by
web hosting companies. Each server has its own IP address. Since IP addresses are difficult
to remember therefore, webmaster points their domain name to the IP address of the server
their website is stored on.
It is not possible to host your website on your local computer, to do so you would have to
leave your computer on 24 hours a day. This is not practical and cheaper as well. This is
where web hosting companies comes in.
Types of Hosting
The following table describes different types of hosting that can be availed as per the need:
S.N. Hosting Description
1. Shared Hosting
In shared hosting, the hosting company puts thousand of website on the same physical server.
Each customer has their own allocation of physical web space and a set of bandwidth limit. As all
websites share same physical memory, MYSQL server and Apache server, one website on the
server experiencing high traffic load will affect performance of all websites on the server.
2. Virtual Private Server (VPS)
It is also known as Virtual Dedicated Server. It is a server which is partitioned into smaller servers.
In this customer is given their own partition, which is installed with its own operating system.
Unlike shared hosting, VPS doesn’t share memory or processor time rather it allocates certain
amount of memory and CPU to use which means that any problem on a VPS partition on the same
drive will not affect other VPS customers.
3. Dedicated Server
In this kind of hosting, single dedicated server is setup for just one customer. It is commonly used
by the businesses that need the power, control and security that a dedicated server offers.
4. Reseller Hosting
A reseller acts as a middle man and sells hosting space of someone else’s server.

24. 5. Grid Hosting
Instead of utilizing one server, Grid Hosting spreads resources over a large number of servers. It is
quite stable and flexible. The servers can be added or taken away from the grid without crashing
the system.
Web Hosting Companies
Following are the several companies offering web hosting service:
S.N. Hosting Company
1. Blue Host
2. Go Daddy
3. Host Gator
4. just Host
5. Laughing Squid
6. Hivelocity
7. liquid Web
8. Media TempleServInt
9. Wired Tree
10. Wild West Domains
11. Wix
12. WIPL
13. Big Rock
What is website maintenance?
Website maintenance is the process of keeping a website up-to-date and running
smoothly as well as performing optimally. Website maintenance includes tasks like

25. ensuring all the links on your site are working, regularly updating content, and fixing
any broken links. It also involves more general housekeeping tasks like backing up
your site regularly and monitoring your site's performance.
11 Types of website maintenance
After you launch a website, it's important to regularly perform web maintenance to
prevent any technical issues, improve the user experience, and ensure your site
continues to rank high in search engine results pages (SERPs). Website
maintenance can be daunting, but keeping your site running smoothly is essential.
There are a few different types of website maintenance that you should be aware of:
1. Security updates
Security patches are released by web development companies to address
vulnerabilities in their software. Patches are essential in keeping your site safe from
hackers, so installing them as soon as they're available is important.
2. Plugin and theme updates
Plugins and themes help to extend the functionality of your website. But like any
software, they need to be kept up-to-date to ensure compatibility with the latest web
browsers and security patches.
3. Content updates
Your website's content should be kept up-to-date to ensure that it is relevant and
accurate. This includes adding new blog posts, updating product descriptions, and
removing outdated content. Outdated content can make your site look
unprofessional and can turn away potential customers.
4. Backup and disaster recovery
Having a recent backup of your website is important in case something goes wrong.
Disaster recovery planning helps ensure that you can quickly get your website back
up and running in the event of a major problem. A backup helps to prevent data loss
and ensures that you can restore your site if it's ever hacked or corrupted.
5. Performance monitoring and optimization
Monitoring your website's performance can help you identify potential problems and
take steps to keep your site running smoothly. Optimizing your website's
performance can help improve your site's speed and responsiveness. It entails the
tasks of improving web page loading times, optimizing image sizes, and minifying
code.
6. Security scanning

26. Security scanning is important in web maintenance to ensure that the site is secure
from any potential threats. Regularly scanning the website can identify and fix
security vulnerabilities before they cause any damage. This helps to protect both the
website and its users from potential harm.
Scanning the website also helps to improve the user experience. By identifying and
fixing potential security vulnerabilities, users can be assured that their personal
information is safe when using the website.
Introduction
Search Engine refers to a huge database of internet resources such as web pages,
newsgroups, programs, images etc. It helps to locate information on World Wide Web.
User can search for any information by passing query in form of keywords or phrase. It then
searches for relevant information in its database and return to the user.

Search Engine Components
Generally there are three basic components of a search engine as listed below:
1. Web Crawler

27. 2. Database
3. Search Interfaces
Web crawler
It is also known as spider or bots. It is a software component that traverses the web to gather
information.
Database
All the information on the web is stored in database. It consists of huge web resources.
Search Interfaces
This component is an interface between user and the database. It helps the user to search
through the database.
Search Engine Working
Web crawler, database and the search interface are the major component of a search engine
that actually makes search engine to work. Search engines make use of Boolean expression
AND, OR, NOT to restrict and widen the results of a search. Following are the steps that are
performed by the search engine:
 The search engine looks for the keyword in the index for predefined database
instead of going directly to the web to search for the keyword.
 It then uses software to search for the information in the database. This
software component is known as web crawler.
 Once web crawler finds the pages, the search engine then shows the relevant
web pages as a result. These retrieved web pages generally include title of
page, size of text portion, first several sentences etc.
These search criteria may vary from one search engine to the other. The retrieved information is
ranked according to various factors such as frequency of keywords, relevancy of information,
links etc.
 User can click on any of the search results to open it.
Architecture
The search engine architecture comprises of the three basic layers listed below:
 Content collection and refinement.
 Search core
 User and application interfaces

28. Search Engine Processing
Indexing Process
Indexing process comprises of the following three tasks:
 Text acquisition
 Text transformation
 Index creation
Text acquisition
It identifies and stores documents for indexing.
Text Transformation
It transforms document into index terms or features.
Index Creation
It takes index terms created by text transformations and create data structures to suport fast
searching.
Query Process
Query process comprises of the following three tasks:
 User interaction
 Ranking
 Evaluation
User interaction
It supporst creation and refinement of user query and displays the results.

29. Ranking
It uses query and indexes to create ranked list of documents.
Evaluation
It monitors and measures the effectiveness and efficiency. It is done offline.
Examples
Following are the several search engines available today:
Search
Engine
Description
Google It was originally called BackRub. It is the most popular search engine globally.
Bing It was launched in 2009 by Microsoft. It is the latest web-based search engine that also
delivers Yahoo’s results.
Ask It was launched in 1996 and was originally known as Ask Jeeves. It includes support for
match, dictionary, and conversation question.
AltaVista It was launched by Digital Equipment Corporation in 1995. Since 2003, it is powered
by Yahoo technology.
AOL.Search It is powered by Google.
LYCOS It is top 5 internet portal and 13th largest online property according to Media Matrix.
Alexa It is subsidiary of Amazon and used for providing website traffic information.
Internet Security

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Introduction
Internet security refers to securing communication over the internet. It includes specific
security protocols such as:
 Internet Security Protocol (IPSec)
 Secure Socket Layer (SSL)
Internet Security Protocol (IPSec)

30. It consists of a set of protocols designed by Internet Engineering Task Force (IETF). It
provides security at network level and helps to create authenticated and confidential packets
for IP layer.
Secure Socket Layer (SSL)
It is a security protocol developed by Netscape Communications Corporation. ). It provides
security at transport layer. It addresses the following security issues:
 Privacy
 Integrity
 Authentication
Threats
Internet security threats impact the network, data security and other internet connected
systems. Cyber criminals have evolved several techniques to threat privacy and integrity of
bank accounts, businesses, and organizations.
Following are some of the internet security threats:
 Mobile worms
 Malware
 PC and Mobile ransomware
 Large scale attacks like Stuxnet that attempts to destroy infrastructure.
 Hacking as a Service
 Spam
 Phishing
Email Phishing
Email phishing is an activity of sending emails to a user claiming to be a legitimate
enterprise. Its main purpose is to steal sensitive information such as usernames, passwords,
and credit card details.
Such emails contains link to websites that are infected with malware and direct the user to
enter details at a fake website whose look and feels are same to legitimate one.
What a phishing email may contain?
Following are the symptoms of a phishing email:
Spelling and bad grammar
Most often such emails contain grammatically incorrect text. Ignore such emails, since it can
be a spam.
Beware of links in email
Don’t click on any links in suspicious emails.
Threats
Such emails contain threat like “your account will be closed if you didn’t respond to an email
message”.

31. Spoofing popular websites or companies
These emails contain graphics that appear to be connected to legitimate website but they
actually are connected to fake websites.
Firewall Security

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Firewall is a barrier between Local Area Network (LAN) and the Internet. It allows keeping
private resources confidential and minimizes the security risks. It controls network traffic, in
both directions.
The following diagram depicts a sample firewall between LAN and the internet. The
connection between the two is the point of vulnerability. Both hardware and the software can
be used at this point to filter network traffic.

There are two types of Firewall system: One works by using filters at the network layer and the
other works by using proxy servers at the user, application, or network layer.
Key Points
 Firewall management must be addressed by both system managers and the
network managers.
 The amount of filtering a firewall varies. For the same firewall, the amount of
filtering may be different in different directions.

33. 1) What is the role of TCP ? How packet/data is transferred from end-to-
end user ? Explain.
TCP organizes data so that it can be transmitted between
a server and a client. It guarantees the integrity of the data
being communicated over a network.
TCP 3-Way Handshake Process read for end to end user


2) What is crawling ?
Crawling refers to following the links on a page to new pages, and continuing
to find and follow links on new pages to other new pages

3) Explain the FTP process model with suitable diagram.
Mechanism of File Transfer Protocol
Types of Connection in FTP
1. Control Connection
2. Data Connection
1. Control Connection: For sending control information like user
identification, password, commands to change the remote
directory, commands to retrieve and store files, etc., FTP makes
use of a control connection. The control connection is initiated on
port number 21.
2. Data connection: For sending the actual file, FTP makes use
of a data connection. A data connection is initiated on port number
20.

34. 4) What do you mean by op(on nega(on in TELNET?
Option negotiation is the process of both the client and server agreeing to a
common set of features also known as options that will be supported by both the
client and server terminals.

5) Discuss terminal Emula(on. Also write down the port number of FTP.
A terminal emulator, or terminal application, is a computer
program that emulates a video terminal within some other display architecture. Though
typically synonymous with a shell or text terminal, the term terminal covers all remote
terminals, including graphical interfaces
FTP uses ports 20 and 21 to transfer files between a client and a server.

6) Write down different services of TELNET.
 Communication Services
 Information Retrieval Services
 File Transfer
 World Wide Web Services
 Web Services
 Directory Services
 Automatic Network Address Configuration
 Network Management Services
 Time Services
 Usenet
 NewsGroup
 Ecommerce

7) How does TELNET accommodate heterogeneity?


8) What are the most commonly implemented TELNET op(ons?


9) Write are the func(ons of these control func(ons?
AO,AYT,SYNCH,AY,BRK

35. Q.WHAT IS RFC.WHY RFC IS WRITTEN .SAMPLE RFC FOR NEWLY DESIGNED
SOFTWARE FOR MESSAGE TRANSFER RFC stands for Request for Comments. It
is a document published by the Internet Engineering Task Force (IETF) that describes
proposed standards, protocols, procedures, and other relevant informa"on related to
the Internet and computer networking. RFCs are used to document and
communicate specifica"ons, ideas, and best prac"ces within the technical
community.

RFCs are wri%en for various reasons, including:
Standardiza"on: RFCs are used to define standards for protocols, technologies, and
methodologies to ensure interoperability and compa"bility across different systems
and networks.
Informa"onal Purposes: RFCs are o+en wri%en to provide valuable informa"on,
guidelines, and best prac"ces to the technical community on various topics related to
the Internet and networking.

Experimental or Research Purposes: RFCs can be used to propose new ideas,
protocols, or technologies for experimenta"on or research purposes. These RFCs
may not necessarily become widely adopted standards.
Community Feedback: RFCs provide a mechanism for gathering feedback,
sugges"ons, and improvements from the technical community. They allow for open
discussion and collabora"on before finalizing a standard or protocol.

10) Write difference between POP and IMAP.


11) What Is E-mail client?

36. An email client is also known as a Mail User Agent. It is
actually the program or the application that one has on his/her
computer to send and receive emails. The email client is used to
compose emails, send them, and read them. It is basically used
for email management like creating, sending, receiving, and
deleting emails

12) What is the difference between a URL, Domain, Subdomain,
Hostname etc.?
A URL (Uniform Resource Locator) is a unique identifier
used to locate a resource on the Internet. It is also referred to
as a web address.
A domain name is the part of your Internet address that comes after "www" an
example for domain name;
www.google.com, www.yahoo.com
In this “yahoo.com” is called domain name
A subdomain name is a piece of additional information added
to the beginning of a website's domain name

A hostname (archaically nodename) is a label that is assigned
to a device connected to a computer network and that is used
to identify the device in various forms of electronic
communication, such as the World Wide Web.

13) Write down name of E-mail client.
Microsoft Outlook, Gmail, Thunderbird:, Apple Mail,,
ProtonMail

14) What do you mean by E-mail rou(ne?
Email routing is the process of ensuring that the right messages get to the
right recipients. It allows users to send different types of emails to separate accounts
based on criteria such as the recipient's address or department.

15) IP Addresses Explain.

37. What is the use of an IP address? An IP address identifies every device
connected to the internet. This enables computers and other internet-connected
devices, such as mobile phones and Internet-of-Things
The classes of IPv4 addresses
The different classes of the IPv4 address are the following:
1) Class A address
2) Class B address
3) Class C address
4) Class D address
5) Class E address

Class A Address
The first bit of the first octet is always set to zero. So that the first octet ranges from
1 – 127. The class A address only include IP starting from 1.x.x.x to 126.x.x.x. The IP
range 127.x.x.x is reserved for loop back IP addresses. The default subnet mask for
class A IP address is 255.0.0.0. This means it can have 126 networks (2
7
-2) and
16777214 hosts (2
24
-2). Class A IP address format is
thus: 0NNNNNNN .HHHHHHHH.HHHHHHHH.HHHHHHHH.

Class B Address
Here the first two bits in the first two bits is set to zero. Class B IP Addresses range
from 128.0.x.x to 191.255.x.x. The default subnet mask for Class B is 255.255.x.x.
Class B has 16384 (2
14
) Network addresses and 65534 (2
16
-2) Host addresses. Class
B IP address format is: 10NNNNNN.NNNNNNNN .HHHHHHHH.HHHHHHHH

Class C Address
The first octet of this class has its first 3 bits set to 110. Class C IP addresses range
from 192.0.0.x to 223.255.255.x. The default subnet mask for Class C is
255.255.255.x. Class C gives 2097152 (2
21
) Network addresses and 254 (2
8
-2) Host
addresses. Class C IP address format
is: 110NNNNN.NNNNNNNN.NNNNNNNN .HHHHHHHH

38. Class D Address
The first four bits of the first octet in class D IP address are set to 1110. Class D has
IP address rage from 224.0.0.0 to 239.255.255.255. Class D is reserved for
Multicasting. In multicasting data is not intended for a particular host, but multiple
ones. That is why there is no need to extract host address from the class D IP
addresses. The Class D does not have any subnet mask.

Class E Address
The class E IP addresses are reserved for experimental purpose only for R&D or
study. IP addresses in the class E ranges from 240.0.0.0 to 255.255.255.254. This
class too is not equipped with any subnet mask.
The features of IPv6
The main features of the IPv6 are listed below.
1) IPv6 provides better end-to-end connectivity than IPv4.
2) Comparatively faster routing.
3) IPv6 offers ease of administration than IPv4.
4) More security for applications and networks.
5) It provides better Multicast and Anycast abilities.
6) Better mobility features than IPv4.
7) IPv6 follows the key design principles of IPv4 and so that the transition from IPv4
to IPv6 is smoother.
16.WRITE DOWN DIFFERENT EMAIL PROTOCOLS
ANS. The common protocols for email delivery are Post Office Protocol (POP),
Internet Message Access Protocol (IMAP), and Simple Mail Transfer Protocol (SMTP).
Each of these protocols has a standard methodology to deal with the emails and also
has defined func"ons.
POP Protocol:
POP stands for Post Office Protocol. Email clients use the POP protocol support in
the server to download the emails. This is primarily a one-way protocol and does not
sync back the emails to the server.

39. IMAP Protocol :
IMAP stands for Internet Message Access Protocol. IMAP Protocol is used to sync the
emails in the server with the email clients. It allows two-way sync of emails between
the server and the email client, while the emails are stored on the server.

SMTP Protocol :
SMTP stands for Simple Mail Transfer
Protocol. SMTP is the principal email protocol that
is responsible for the transfer of emails between email clients and email servers