Computer Network Notes for SSC Exams: LAN, WAN, Topologies and Devices

Computer networks are asked every year in SSC Computer Knowledge. The questions are about the types of networks, the topologies and the work of devices such as a router, a switch and a modem. These computer network notes for SSC explain them with tables and practice questions. Read it with the Internet and Networking Notes and Internet Protocols Notes notes.

What Is a Computer Network?

A computer network is a group of computers and devices connected to share data and resources such as files, printers and the internet. Each computer or device in a network is called a node.

Types of Networks

Network Topologies

Network Devices

Transmission Media and Terms

• Guided media (wired): twisted pair cable, coaxial cable and optical fibre. Optical fibre is the fastest and uses light.
• Unguided media (wireless): radio waves, microwaves, infrared, satellite and Wi-Fi.
• Bandwidth is the amount of data that can be sent in a given time (bits per second).
• An IP address identifies every device on a network, and a MAC address is the unique hardware address of a NIC.
• Client-server model: a client requests and a server provides the service.

History of Networks

Network Types in More Detail

• PAN connects personal devices within about 10 metres (Bluetooth).
• LAN covers a building and uses Ethernet or Wi-Fi. It has a high speed and is owned by one organisation.
• CAN (Campus Area Network) connects the LANs of a university or a campus.
• MAN covers a city and can connect many LANs.
• WAN covers countries using leased lines, satellites or the internet.
• VPN (Virtual Private Network) makes a secure private network over the public internet.
• Intranet is a private network of an organisation using internet technology; extranet gives limited access to outside partners; the internet is the public global network.
• SAN (Storage Area Network) connects the storage devices to the servers.

Network Models

Switching Techniques

Transmission Media in Detail

• The transmission modes are simplex (one direction only, such as a keyboard or a TV broadcast), half-duplex (both directions but one at a time, such as a walkie-talkie) and full-duplex (both directions at the same time, such as a phone call).
• Bandwidth is the capacity of a channel. Latency is the delay in the transfer of data.

Wireless Technology and Mobile Generations

Important Questions Explained

Question 1: Which network covers a school or an office building?
Answer: A LAN (Local Area Network).

Question 2: Which is the largest network in the world?
Answer: The internet, which is a WAN.

Question 3: Which device connects two different networks and finds the best path?
Answer: A router.

Question 4: Which topology uses a central hub or switch?
Answer: The star topology.

Question 5: Which transmission medium is the fastest?
Answer: Optical fibre.

Question 6: Which device converts digital signals into analog and back?
Answer: A modem.

Quick Tips to Remember

• Remember the area order: PAN, LAN, MAN, WAN.
• Link star topology with a central hub or switch.
• Remember router for connecting networks and switch for connecting devices inside a LAN.
• Learn that a modem stands for modulator-demodulator.
• Optical fibre means light and the highest speed.

Common Mistakes to Avoid

• Mixing the hub and the switch.
• Confusing a router with a modem.
• Writing the bus topology as having a central device.
• Writing the internet as a LAN.
• Mixing the IP address and the MAC address.

Quick Revision Points

• LAN = small area; MAN = city; WAN = country or world.
• Star topology = central hub; bus = single cable; ring = circle; mesh = all connected.
• Router = connects networks; switch = smart LAN device; hub = broadcasts; modem = signal converter.
• Optical fibre is the fastest guided medium.
• IP address identifies a device; MAC address is the hardware address.

Practice Questions With Answers

1. The internet is an example of which network?
   Answer: WAN (Wide Area Network).
2. A network in one building is called?
   Answer: LAN (Local Area Network).
3. Which topology uses a central hub?
   Answer: Star (Most common).
4. Which device finds the best path for data?
   Answer: Router (Connects networks).
5. Which device converts digital to analog signals?
   Answer: Modem (Modulator-demodulator).
6. Which medium uses light signals?
   Answer: Optical fibre (Fastest wired medium).
7. Which topology connects each device to every other?
   Answer: Mesh (Most reliable).
8. What does NIC stand for?
   Answer: Network Interface Card (Connects a PC to a network).
9. A device that strengthens the signal is?
   Answer: Repeater (Long distance).
10. What is a unique hardware address of a NIC?
    Answer: MAC address (Physical address).

More Practice Questions With Answers

1. Who invented Ethernet?
   Answer: Robert Metcalfe (1973).
2. Which was the first packet-switching network?
   Answer: ARPANET (1969).
3. Which transmission mode allows two-way communication at the same time?
   Answer: Full duplex (Phone call).
4. Which is the one-way transmission mode?
   Answer: Simplex (Keyboard).
5. Which switching is used on the internet?
   Answer: Packet switching (Packets).
6. Which model has all computers equal?
   Answer: Peer-to-peer (P2P).
7. When did VSNL start the public internet in India?
   Answer: 1995 (15 August).
8. Which private network of a company uses internet technology?
   Answer: Intranet (Organisation).
9. Which cable carries data as light?
   Answer: Optical fibre (Fastest).
10. Which network connects the LANs of a campus?
    Answer: CAN (Campus area network).
11. What is the full form of VPN?
    Answer: Virtual Private Network (Secure).
12. Which generation of mobile network first gave mobile internet and video calls?
    Answer: 3G (2000s).

How to Practise This Chapter

1. Read the tables once and learn the key facts by heart.
2. Revise the quick revision points the next day.
3. Attempt the practice questions above without looking at the answers.
4. Solve a full SSC CGL Tier 1 mini mock to test your general awareness.
5. Check the previous year papers to see how SSC asks computer questions.

Related Notes and Practice Papers

• Internet Protocols Notes
• Internet and Networking Notes
• Email, Browser and Search Engine Notes
• Computer Knowledge Notes for SSC
• SSC CGL Tier 1 Mini Mock

Explore More SSC Subjects

SSC exams test many subjects, so connect this topic with the related subjects below:

• General Science Notes
• General Awareness Notes
• Quantitative Aptitude Notes
• Reasoning Notes
• Electrical Engineering (SSC JE) Notes
• All SSC subjects and notes

Frequently Asked Questions

What is a computer network?

A computer network is a group of connected computers and devices that share data and resources.

What is the difference between LAN, MAN and WAN?

A LAN covers a small area like a building, a MAN covers a city and a WAN covers a country or the world.

What is a topology?

A topology is the arrangement of the devices in a network, such as bus, star, ring and mesh.

Which topology is the most common in LANs?

The star topology is the most common in LANs.

What is the difference between a hub and a switch?

A hub sends data to all the devices, while a switch sends data only to the intended device.

What does a router do?

A router connects different networks and finds the best path for the data.

What is a modem?

A modem converts digital signals into analog signals and back so that a computer can use telephone or cable lines.

Which transmission medium is the fastest?

Optical fibre is the fastest wired medium.

How many questions come from networking in SSC exams?

One or two questions usually come from networks and the internet.

What is the difference between the internet and an intranet?

The internet is a public global network, while an intranet is a private network of one organisation that uses the same technology.

What is packet switching?

In packet switching the data is divided into small packets that are sent separately and joined at the destination. The internet works in this way.

What is the difference between simplex, half-duplex and full-duplex?

Simplex sends data in one direction only, half-duplex in both directions but one at a time, and full-duplex in both directions at the same time.