CBSE Class XII Computer Science Notes

1.1 Modem (Modulator-Demodulator)

A Modem converts signals to analog and analog to digital. We use a Modem for internet connectivity via telephone lines. For example we have DSL modem and cable modem.

1.2 Hub

A Hub is a Networking Device that connects multiple computers. It works on the Physical Layer. When a Hub gets data it sends this data to all devices. This is not very efficient. A Hub does not filter data.

1.3 Switch

A Switch is more advanced than a Hub. It works on the Data Link Layer. A Switch sends data to the device that needs this data. It uses the devices MAC address to do this. This makes the network more efficient.

1.4 Router

A Router connects networks like a Local Area Network to the Internet. It works on the Network Layer. A Router uses IP addresses to send data to the place. For example we use a Home Wi-Fi router.

1.5 Repeater

A Repeater helps when signals are weak. It regenerates these signals. We use a Repeater to extend the distance of a network.

1.6 Bridge

A Bridge connects networks that’re similar. It filters traffic based on the MAC address of devices.

1.7 Gateway

A Gateway acts like a protocol converter. It helps different networks communicate with each other. For example it connects a Local Area Network with networks.

1.8 Access Point (AP)

An Access Point provides connectivity, like Wi-Fi. It extends a wired network into a network.

The way devices are set up in a network is called the network topology.

Network topology is the way devices are arranged in a network.

2.1 Bus Topology

• All the devices in a bus topology are connected to one cable.
• The main advantages of a bus topology are that it is easy to set up. It does not cost a lot of money.
• The disadvantages of a bus topology are that if the main cable fails the whole network will stop working and it is hard to find faults.

2.2 Star Topology

• In a star topology all the devices are connected to a device.
• The advantages of a star topology are that it is easy to manage and if there is a fault it’s easy to find.
• The disadvantages of a star topology are that if the central device fails the whole network will stop working and more cables are needed.

2.3 Ring Topology

• In a ring topology the devices are connected in a circle.
• The data in a ring topology travels in one direction.
• The advantages of a ring topology are that the data does not collide with each other.
• The disadvantages of a ring topology are that if one device fails the whole network will be affected.

2.4 Mesh Topology

• In a mesh topology every device is connected to every device.
• The advantages of a mesh topology are that it is very reliable and there is no loss of data.
• The disadvantages of a mesh topology are that it is expensive and the installation is complex.

2.5 Tree Topology

• A tree topology is a combination of a star topology and a bus topology.
• It has a structure and it is used in large networks.
• Network topology like tree topology is used for networks.

2.6 Hybrid Topology

• A hybrid topology is a combination of two or more network topologies.
• The hybrid topology is flexible. It can be scaled up.
• Network topology, like hybrid topology is very flexible and scalable.

3.1 HTTP (HyperText Transfer Protocol)

• We use HTTP to move web pages from one place to another.
• It works on something called port 80.

3.2 HTTPS (Secure HTTP)

• This is like HTTP. It is more secure.
• It uses something called encryption to keep things like SSL/TLS.
• It works on port 443.

3.3 FTP (File Transfer Protocol)

• We use FTP to move files over the Network.
• To use it we need to login with our username and password.

3.4 SMTP (Simple Mail Transfer Protocol)

• We use SMTP to send emails to our friends.

3.5 POP3 (Post Office Protocol)

• We use POP3 to get emails from the server and download them to our computer.

3.6 IMAP (Internet Message Access Protocol)

• IMAP lets us look at our emails on the server without downloading them.
• Our emails stay on the server so we can see them from any device.

3.7 TCP/IP (Transmission Control Protocol / Internet Protocol)

• TCP/IP is the base of how the internet works.
• TCP makes sure our data gets to where it needs to go
• IP helps figure out where our data needs to go and how to get it there.

3.8 UDP (User Datagram Protocol)

• UDP is faster than TCP. It is not as good at making sure our data gets to where it needs to go.
• We use UDP when we are streaming videos or playing games online.

3.9 DNS (Domain Name System)

• DNS helps us use easy to remember names, like google.com of hard to remember IP addresses.
• For example when we type google.com it uses DNS to find the IP address of the google server.