The document provides information on various computer networking concepts. It defines Internet of Things (IoT) and discusses the differences between public and private clouds. It also describes wired and wireless networks, the roles of clients and servers, and common networking hardware like NICs, switches, routers and access points. The document further explains networking protocols and standards such as IP versions, DNS, URLs, modulation techniques, and communication protocols like HTTP, FTP, SMTP and more.

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COMPUTER SCIENCE – NEW (083)
CLASS - XII
Unit 2: Computer Networks (CN)
Revision Notes by https://www.pyforschool.com
IOT
Internet of things is essentially a platform where embedded devices are connected to the
internet, so they can collect and exchange data with each other. Examples are Smart Mobiles,
smart refrigerators, smart watches, smart fire alarm, smart door lock, medical sensors, fitness
trackers, smart security system
PUBLIC VS. PRIVATE CLOUD
Public Cloud
Public clouds are owned and operated by a third party. Accessed via the web, common public
clouds include Google, Microsoft Azure, AppEngine, and IBM’s Blue Cloud.
Benefits of public cloud computing are ease of access, low cost, and complete lack of
maintenance. Organizations frequently use public clouds for web-based email, online office
applications, storage, and testing and development environments.
Private Cloud
Private cloud owned exclusively by an organization and maintained on a private network with
hardware and software solely dedicated to a single business
Private clouds offer the security and customizable infrastructure not available on public clouds.
It is used by government agencies, financial institutions, and other businesses looking for
enhanced control over their cloud-based environment.
WIRED AND WIRELESS NETWORKS
A wired network uses cables to connect devices, such as laptop or desktop computers, to the
Internet or another network.
A wireless network allows devices to access your network resources from any location within
your wireless network's coverage area or from any Wi-Fi hotspot.

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CONCEPT OF A CLIENT AND SERVER
In client server computing, the client requests a resource and the server provides that resource.
A server may serve multiple clients at the same time while a client is in contact with only one
server. Both the client and server usually communicate via a computer network.
NIC
A network interface card (NIC) is a hardware component without which a computer cannot be
connected over a network. It is a circuit board installed in a computer that provides a dedicated
network connection to the computer. It is also called network interface controller, network
adapter or LAN adapter.
SWITCH/HUB
A small hardware device that joins multiple computers together within a LAN.
REPEATER
An electronic device that amplifies the received signal and then retransmits it on the network
ROUTER
Network device that connects two networks with different protocols.
Router is a device that helps in decision making for data routes.
It works in network layer.
It has a dynamically updating routing table according to which it routes the data.
It can work on LANs and WANs.
It routes the data based on IP addresses.
ROUTING TABLE
In computer networking a routing table is a data table stored in a router that lists the routes to
particular network destinations.
ACCESS POINT
An access point is a device that creates a wireless local area network, usually in an office or
large building. An access point connects to a wired router, switch, or hub via an Ethernet cable,
and projects a Wi-Fi signal to a designated area.

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AMPLITUDE MODULATION
A type of modulation where the amplitude of the carrier signal is modulated (changed) in
proportion to the message signal while the frequency and phase are kept constant.
FREQUENCY MODULATION
It is a type of modulation where the frequency of the carrier signal is modulated (changed) in
proportion to the message signal while the amplitude and phase are kept constant.
COLLISION IN WIRELESS NETWORKS
A network collision occurs when two or more devices attempt to transmit data over a network
at the same time.
Carrier Sense Multiple Access/with Collision Avoidance (CSMA/CA) works to avoid collisions
prior to their occurrence.
CSMA/CA increases network traffic as it requires sending out a signal to the network even
before transmitting any real data. This is to listen for any collision scenarios in the network and
to inform other devices not to transmit.
MAC ADDRESS
A media access control address (MAC address) is a unique identifier assigned to a network
interface controller (NIC) for use as a network address in communications within a network
segment. This use is common in Ethernet, Wi-Fi, and Bluetooth.
IPV4
IPv4 was the first version of IP. It was deployed for production in the ARPANET in 1983. Today it
is most widely used IP version. It is used to identify devices on a network using an addressing
system.
The IPv4 uses a 32-bit address scheme allowing to store 2^32 addresses which is more than 4
billion addresses. Till date, it is considered the primary Internet Protocol and carries 94% of
Internet traffic.
IPV6
It is the most recent version of the Internet Protocol. Internet Engineer Taskforce initiated it in
early 1994. The design and development of that suite is now called IPv6.

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This new IP address version is being deployed to fulfill the need for more Internet addresses. It
was aimed to resolve issues which are associated with IPv4. With 128-bit address space, it
allows 2^128 unique address space. IPv6 also called IPng (Internet Protocol next generation).
DNS (DOMAIN NAME SYSTEM)
The Internet's system for converting alphabetic names into numeric IP addresses. For example,
when a Web address (URL) is typed into a browser, DNS servers return the IP address of the
Web server associated with that name.
WEB URLS,
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. URLs consist of multiple parts -- including a
protocol and domain name -- that tell a web browser how and where to retrieve a resource.
2G
They used digital signals for transmissions of voice. 2G enabled the mobile systems to provide
paging, SMS, voicemail and fax services.
3G
The 3G technology adds multimedia facilities to 2G phones by allowing video, audio, and
graphics applications.
4G
4G provides better-than-TV quality images and video-links.
WIFI
Wireless Fidelity
TRACEROUTE
Traceroute is a command which can show you the path a packet of information takes from your
computer to one you specify. It will list all the routers it passes through until it reaches its
destination, or fails to and is discarded. In addition to this, it will tell you how long each 'hop'
from router to router takes.
PING

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Ping is a computer network administration software utility used to test the reachability of a
host on an Internet Protocol network.
IPCONFIG
In computing, ipconfig is a console application of some operating systems that displays all
current TCP/IP network configuration values and refresh Dynamic Host Configuration Protocol
and Domain Name System settings.
NSLOOKUP
nslookup is a network administration command-line tool available in many computer operating
systems for querying the Domain Name System to obtain domain name or IP address mapping,
or other DNS records.
WHOIS
WHOIS is a query and response protocol that is widely used for querying databases that store
the registered users or assignees of an Internet resource, such as a domain name, an IP address
block or an autonomous system.
SPEED-TEST
The speed test can be conducted by an end-user to determine the upload and download speed
of a network. It can be a mobile data network or WIFI. There are several factors affecting speed
test, such as: Device, Network service, Servers
HTTPS
Hypertext Transfer Protocol Secure is a secure version of the HTTP protocol that uses the
SSL/TLS protocol for encryption and authentication.
TELNET
Telnet is the main internet protocol for creating a connection with a remote machine. It allows
you to connect to remote computers (called remote hosts) over a TCP/IP network (such as the
Internet).
HTTP
HTTP is the protocol that is used for transferring hypertext (i.e. text, graphic, image, sound,
video etc.) between two computers and is particularly used on the World Wide Web. It is a

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TCP/IP based communication protocol and provides a standard for Web browsers and servers
to communicate.
FTP
It is used for transferring files from one system to another on the internet.
SCP
Secure copy protocol (SCP) is a means of securely transferring computer files between a local
host and a remote host or between two remote hosts.
SSH
SSH, also known as Secure Shell, is a network protocol that gives users, particularly system
administrators, a secure way to access a computer over an unsecured network.
POP
Post Office Protocol (POP) is a type of computer networking and Internet standard protocol
that extracts and retrieves email from a remote mail server for access by the host machine.
IMAP
The Internet Message Access Protocol (IMAP) is an Internet standard protocol used by email
clients to retrieve email messages from a mail server over a TCP/IP connection.
SMTP
It allows transmission of email over the Internet.
VOIP
VoIP stands for voice over internet protocol. It enables the transfer of voice using packet
switched network rather than using public switched telephone network.
NFC
NFC or Near Field Communication is a protocol that helps two devices communicate wirelessly
when they are placed right next to each other—for instance, smartphones or smart watches.
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