Computer Networks — NCERT Solutions

• In bus topology, each node is connected with the help of a single cable called the bus.
• In star topology, each node is connected to a central switching device through independent cables.

A modem stands for MOdulator DEModulator. It is a device used for conversion between analog signals and digital bits.

It is used because computers store and process data as 0s and 1s, but data must be converted into signals for transmission over a network or while browsing the internet. The modem converts digital data into analog signals at the sender’s end and converts analog signals back into digital data at the receiver’s end.

• Switch: A networking device used to connect multiple computers or communicating devices in a LAN. It reads the destination address in a data packet and sends it only to the required device.
• Repeater: An analog device that regenerates weakened signals on a cable and puts them back on the cable.
• Router: A network device that receives data, analyses it, and transmits it to other networks. It connects a local area network to the Internet.
• Gateway: The entry and exit point of a network that acts as a gate between an organisation’s network and the outside world of the Internet.
• NIC: Network Interface Card, also called Ethernet card; it is a network adapter used to set up a wired network and acts as an interface between the computer and the network.

The significance of a MAC address is that it uniquely identifies a computer or network adapter on a network. It is the physical/hardware address of the NIC, permanently assigned at manufacturing time, and helps in physically identifying the machine on the network.

MAC address and IP address are both unique identifiers, but they differ in the following ways:

• MAC address is the physical or hardware address of the NIC.
• It is permanent and cannot be changed.
• It is used to physically identify a machine on the network.

• IP address is the Internet Protocol address of a node.
• It can change when a node moves from one network to another.
• It is used to uniquely identify a node for communication over a network using Internet Protocol.

Thus, MAC is hardware-based and permanent, while IP is network-based and may change.

DNS stands for Domain Name System. It is the system that converts a domain name into its corresponding IP address.

A DNS server is the server that performs this domain name resolution. When we enter a URL in a browser, the browser contacts the DNS server to find the IP address of that domain name, and then the information is loaded from that IP address.

The Internet is the global network of computing devices such as desktops, laptops, servers, tablets, mobile phones, routers, switches, gateways, and many smart devices. It is the large communication network that connects devices across the world.

The World Wide Web (WWW) or web is an ocean of information stored in the form of interlinked web pages and web resources that are accessed through the Internet.

So, the Internet is the network, while the web is a service on that network.

Examples of the Internet include the worldwide connection used for email, online communication, and connectivity between devices. Examples of the web include websites such as ncert.nic.in, wikipedia.org, and mhrd.gov.in, which are accessed using web pages and URLs.