computer network notes for class 12

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Best computer network notes

class 12 computer science


computer network

what is computer network:-

A computer network is a group of computers which communicate with another computer and share their resources , date and applications.

Types of networks: Local area and wide area

                  LAN                                         WAN

1. LAN stands for local area                 1.WAN stands for wide area
    networks.                                              networks.
2. networks within office or                  2.networks across country or
     building.                                                continent.
3. less congestion.                                  3.more congestion.
4. the speed of LAN is high .                 4.the speed is slower than LAN.


The internet is a ” network of networks’ .internet is means of connecting a computer to any other computer anywhere in the world via dedicated routers and servers.

cloud computing:-

Cloud computing is delivery of computing services like storage, database , networking, software, analytics, and intelligence over the internet.

      Private cloud                                             public cloud

1.  data hosted on a dedicated server.                    1.usages shared server.
2.  management done by business.                        2.maintained by service provider.
3.  secured and high performance.                         3.less secured and average performance
4.  cost is very high.                                               4. free or less charges
5.  ex:-eucalyptus, Ubuntu enterprise                     5. eg:- google drive, Microsoft azure.
      cloud- UEC amazon Vpc, VMware.

iot :-

the internet of things ,
or iot, is system of interrelated computing devices,
mechanical and digital machines, object , animals or people that are provided with unique identifiers(Uids)
and the ability to transfer data over a network without requiring human to – human or human – to – computer interaction .

benefits of iot

1. moniterthier overall business process.
2. improve the customer experience.
3. save time and money
4.enhance employee productivity.

network types

wired network                                         wireless network

1.speed of operation                                         1.lower,compare to wired
    is high.                                                                     network.
2.less costly as cables                                        2.more as wireless devices
    are not expensive.                                                     are expensive.
3.wired network installation                            3.installation is easy and it
    require more time.                                             require less time.
4.copper wires, optical fibre                              4. EM waves or radio waves
     cables are used.                                                   or infrared medium are used
5.LAN(Ethernet),MAN can                                  WLAN, WPAN(Bluetooth),infrared,
     be developed.                                                       cellular(GSM,CDMA,LTE)

client server concept

the client server model describes how a server provides resources and services to one or more clients. Example of servers, mail server, and file server.


A client a program that runs on the local machine requesting service from server ,
ex:- chrome , Mozilla


A server is a program that runs on the remote machine providing services to the clients when the request arrives at the server , then it responds to the request .
ex:- WWW. google . com

networks devices 🙁 NiC, switch , hub, router, access point)

1. NIC :

(network interface card):
Nic is also  referred to as an Ethernet card or network adapter .
A NIc is a computer expansion card for for connecting  to a networks using an Ethernet cable and an RJ-450 connector
RJ45:- registered jack 45

2. Mac address ( media access address ):-

Mac address are unique 48 bit hardware number of computer,
which is embedded into NIC card during the the time of manufacturing.
Mac address is also known as physical address of a network device.


In this type of communication,
data are transmitted through satellite.
Under this arrangement, there is an earth station and a satellite placed in the stationary orbit,
which is about 22300 miles above the earth’s surface. In satellite communication,
the earth station transmits data towards the satellite and the satellite accepts these signals, amplifies them and then retransmits them towards the earth.
These signals are captured by the receiver.

access point:-

a wireless access point is a network devices that transmits and receives data over a wireless local area network(WLAN).the wireless A.P services as enter connection access point services as enter connection point between the WLAN and fixed wired network.


case statements are a powerful tool for control in programming. … The switch
variable/expression is evaluated once.
Switch statement looks up the evaluated variable/expression in the jump table and directly decides which code block to execute.
If no match is found,
then the code under default case is executed.
computer network notes


A hub is a physical layer networking device which is used to connect multiple devices in a network.
They are generally used to connect computers in a LAN.A hub has many ports in it.
A computer which intends to be connected to the network is plugged in to one of these ports.
When a data frame arrives at a port,
it is broadcast to every other port, without considering whether it is destined for a particular destination or not.
computer network notes


a router is device designed to receive,
analyse and forward incoming packets to another network.
A router is connected to at least two networks.

Advantages of Satellite

In satellite communication,
large area could be covered.
This mode of transmission is very useful in multimedia transmission.
Network Topologies
The network topology refers to :-
the arrangement or pattern of computers
(i.e. nodes or workstations), which are interconnected in a network.
Commonly used network topologies are as follows:

1. Bus Topology

Bus topology is also referred as linear topology. Under this arrangement, all nodes in the network are connected by a single length of transmission medium, which is normally a co-axial cable. Both ends of the cable are terminated by terminators. Data transmission from any workstation can travel in both directions.
computer network notes

Advantages of Bus Topology

In bus topology, all nodes are connected through a single length of cable, so very short cable length is used.
Extension of network is very easy in bus topology. We can connect new nodes along its length.

Disadvantages of Bus Topology

When there is any problem in data communication with any node, whole network stops functioning.
In case of any fault in data transmission, fault isolation is very difficult. We have to check the entire network to find the fault.

2. Ring Topology

In ring or circular topology, the nodes are connected in a circular way.
In such arrangement, each node is connected to exactly with its two neighbouring nodes.
* in other words, when the last node in a bus network is connected with first node and the entire network becomes circular network is known as a network using ring topology.
computer network notes

Advantages of Ring Topology

Short cable length is required for connecting the nodes together.
The architecture of network is simple and easy to maintain.

Disadvantages of Ring Topology

In ring topology, each node is connected in a circular way with its two neighbouring nodes, so when there is transmission problem anywhere in the network, entire network stops functioning.
Fault diagnosis is very difficult in a network formed using ring topology.

3. Star Topology

In star topology, there is a direct and dedicated connection of every . node of the network with the central node or server. In star topology, the server is directly connected with each and every node in the network via a hub.

Advantages of Star Topology

The star topology is the most reliable as there is a direct connection of every node in the network with the central node or server.
If there is any problem in connection with any node, other nodes in the network are not affected.
computer network notes

Disadvantages of Star Topology

Since, every node is directly connected with the central node or the server, so a large quantity of the cable is required.
There is dependency on the central node. If there are some problems with the central node, entire network stops functioning.


 The repeater is a hardware device used in a network to amplify the weak signals, when they are transported over long distances. When the signal is transmitted over a line, then due to resistance and other causes it accumulates noise. Due to this noise, the quality of signal degrades.
So, to improve the quality of signals, repeaters are needed to be installed.


network stack:-

a set of network protocol layer that work together. The OSI model that defines seven protocol layers is often called a stack, as is the set of TCP/IP protocols that defines communication aver network.

use of amplitude and frequency modulation

The amplitude modulation and frequency modulation are used to transmit data using the method of modifying a carrier signal.

amplitude modulation                                            frequency modulation

1.frequency and phase remain                                               1.amplitude and phase remain
the same.                                                                                        the same.
2.has poor sound quality.                                                      2.better sound quality.
3.can’t transmit longer                                                          3.higher bandwidth.
4.more susceptible to                                                           4.less susceptible to noise.

Network Protocols

Protocol refers to the set of rules and regulations applicable for a network. The protocol defines standardized format for the data packet to be transmitted through the network, techniques for detecting the errors whenever they arise and methods to correct these errors and so on.
Some of the commonly used protocols are as follows:

1. HTTP (Hyper Text Transfer Protocol)

HTTP is an application level protocol and it is widely used for viewing information of a web page over Internet. It is a generic, stateless and object oriented protocol.
HTTP consists of a set of requests from the browser of a local computer to the web server and a set of responses going back to the other way.
Though HTTP is designed for the use in the web application but it has scope to be used in future object oriented applications.

2. FTP (File Transfer Protocol)

FTP is designed to transfer files from one system to another. Using FTP, different people locating in different geographical locations can cooperate and work on a common project. FTP is designed to promote sharing of files and to encourage the indirect use of remote computers. Using FTP, any type of file can be transferred from one computer to another.

3. TCP/IP (Transmission Control Protocol/Internet Protocol)

TCP/IP is a set of two protocols, i.e. TCP and IP. The Internet Protocol (IP) tells how packets of information are sent out over networks. IP has a packet addressing method that lets any computer on the Internet forward a packet to another computer that is a step closer to the packet’s recipient. The Transmission Control Protocol (TCP) ensures the reliability of data transmission across Internet connected networks. TCP checks packets for errors and submits requests for re-transmission if errors are found.

4. PPP (Point-to-Point Protocol)

The PPP is used with dial-up Internet connections including ISDN. It is a layered protocol, which is used for transmitting the data over usual telephone lines. It can provide connection authentication, transmission, encryption and compression.

Remote Access Software

In remote access software firstly we have to know about the term “remote access”.
Remote access refers to the ability to access a computer or a network from a remote distance. Remote access can be established via a line that runs between a computer and Local Area Network. This type of line provide faster speeds but has the drawback of being more expensive. Another suitable method for performing remote access by establishing a Virtual Private Network, which is usually uses the Internet to connect remote site and users together.
To establish a remote connection, both the local machine and remote computer/server must have remote access software.
Remote access software dial indirectly to the network server.
Team Viewer is one of the example of Remote Access Software. It simplifies remote access over the Internet and supports a wide range of devices. It is free for private uses.


The Internet has gained popularity and emerged as an important and efficient means of communication. The Internet is world wide network of networks.
Through Internet, computers become able to exchange information with each other and find diverse perspective on issue from a global audience.
Basic Components for the Working of Internet
Here, we are discussing some basic yet essential components of a network which are very much required for the proper functioning of the Internet.

IP Address

An IP address is an identifier for a computer or device on a TCP/IP network. It is a way to measure a user’s unique identity.
The traditional IP Addresses (IPv4) uses a 32-bit numeric format and it defines both network and host address.
But now-a-days a new version of the IP protocol (IPv6) has been invented to offer virtually limitless number of unique addresses. An IP address can be static or dynamic.
A static IP address will never change and it is a permanent Internet address. A dynamic IP address is a temporary address that is assigned to any computing device to access the Internet.
An example of IPv4 address is Each number can be from zero to 255.

Types of Routing

Routing is a process which is performed by layer 3 (or network layer) devices in order to deliver the packet by choosing an optimal path from one network to another.

There are 3 types of routing:

1. Static routing –
Static routing is a process in which we have to manually add routes in routing table.

Advantages :–

No routing overhead for router CPU which means a cheaper router can be used to do routing.
It adds security because only administrator can allow routing to particular networks only.
No bandwidth usage between routers.

Disadvantage :–

For a large network, it is a hectic task for administrator to manually add each route for the network in the routing table on each router.
The administrator should have good knowledge of the topology. If a new administrator comes, then he has to manually add each route so he should have very good knowledge of the routes of the topology.


The Domain Name System (DNS) is the phonebook of the Internet. Humans access information online through domain names, like or Web browsers interact through Internet Protocol (IP) addresses. DNS translates domain names to IP addresses so browsers can load Internet resources.


URL stands for Uniform Resource Locator. A URL is nothing more than the address of a given unique resource on the Web. In theory, each valid URL points to a unique resource. Such resources can be an HTML page, a CSS document, an image, etc.
In practice, there are some exceptions, the most common being a URL pointing to a resource that no longer exists or that has moved.
As the resource represented by the URL and the URL itself are handled by the Web server, it is up to the owner of the web server to carefully manage that resource and its associated URL.

TCP:-     (computer network notes)

The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP).
Therefore, the entire suite is commonly referred to as TCP/IP. TCP provides reliable, ordered, and error-checked delivery of a stream of octets (bytes) between applications running on hosts communicating via an IP network.
Major internet applications such as the World Wide Web, email, remote administration, and file transfer rely on TCP, which is part of the Transport Layer of the TCP/IP suite. SSL/TLS often runs on top of TCP.

Network Congestion

Just like in road congestion, Network Congestion occurs when a network is not able to adequately handle the traffic flowing through it. While network congestion is usually a temporary state of a network rather than a permanent feature, there are cases where a network is always congested signifying a larger issue is at hand.

In this section, we will discuss five (5) common causes of network congestion including:

Poor network design/mis-configuration
Over-utilized devices
Faulty devices
Security attack

computer network important questions

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  1. November 9, 2020

    […]  notes of data management      important question of data management (9)computer networks     notes of computer networks    important question of computer network (10)society,law and ethics     notes of society,law […]

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