Artificial Intelligence, Data Analytics and Cyber Security - Laws and Practice · Network Basics and Security

Computer Network Basics, Types, Topologies and Devices

Q: What is the difference between LAN, MAN and WAN?

A LAN covers a building or campus. A MAN covers a city. A WAN covers countries or the world. Speed generally falls and cost rises as coverage grows.

Q: Which network topology is most commonly used today?

The star topology is the most common in offices because it is easy to manage and a single node failure does not affect the rest. Its weakness is the central switch, which is a single point of failure.

Q: What is the difference between a switch and a router?

A switch connects devices within one network and forwards data using MAC addresses. A router connects different networks and forwards data using IP addresses.

Q: Do I need to draw diagrams in the CS Professional exam?

The paper is descriptive. A simple labelled diagram can help explain a topology, but clear points and a case-based conclusion earn the marks.

Updated 11 October 2026 · Fact-checked

A computer network is a group of computers and devices linked to share data and resources. Networks are classed by size (PAN, LAN, MAN, WAN), arranged in topologies (bus, star, ring, mesh, tree) and joined by devices such as hubs, switches, bridges, routers and gateways. In exams, define, compare and give business examples.

Understand Computer Network Basics and Types

A computer network is two or more computing devices connected by a medium so that they can exchange data and share resources such as files, printers, internet access and applications. The connected devices are called nodes. A node can be a computer, a server, a printer or a phone.

Every network has four basic parts: the nodes (sender and receiver), the transmission medium (wired such as twisted pair, coaxial or optical fibre; wireless such as radio waves, Wi-Fi or Bluetooth), the network devices that direct traffic, and the protocols, which are the agreed rules for communication. Without protocols, two devices cannot understand each other even if they are physically connected.

Networks are classified by geographic reach. A PAN (Personal Area Network) covers a few metres around one person, for example a phone linked to earbuds by Bluetooth. A LAN (Local Area Network) covers a building or campus, such as an office in Pune. A MAN (Metropolitan Area Network) covers a city or large town, such as a bank linking its branches across Mumbai. A WAN (Wide Area Network) covers cities, countries or the world. The internet is the best-known WAN.

A topology is the layout of the network. In a bus all nodes share one cable. In a star every node connects to a central device. In a ring each node connects to two neighbours in a closed loop. In a mesh nodes connect to many or all others. A tree is a hierarchy of star networks. Each layout trades off cost, reliability and ease of fault-finding.

Network devices decide how data moves. A hub repeats data to all ports. A switch sends data only to the intended port. A bridge joins two LAN segments. A router forwards data between different networks using IP addresses. A gateway connects networks that use different protocols. For a company secretary, this matters because the security and compliance risks differ by network type and design.

Key rules to remember

Classification by size: PAN (personal, few metres) < LAN (building or campus) < MAN (city) < WAN (country or world); Use this order to answer any comparison question. Range, cost and speed differences follow from it.
Mesh links needed (full mesh): Links = n(n − 1) ÷ 2; n is the number of nodes. Each node needs n − 1 ports. Use it to show why full mesh is costly.
Device and OSI layer: Hub: Layer 1 | Switch and bridge: Layer 2 | Router: Layer 3 | Gateway: up to Layer 7; A basic switch works on MAC addresses. A router works on IP addresses.
Topology failure point: Bus: main cable | Star: central device | Ring: any node or link (single ring) | Mesh: none single; Almost every topology question asks about the effect of one failure.

How to solve Computer Network Basics and Types questions

Use this method for definition, comparison, case-based or short-note questions on networks.

1Read the question and mark the verb: define, differentiate, explain or advise.
2Define the term in one line, naming nodes, medium and sharing of resources where relevant.
3State the classification basis (area covered, layout or function of the device).
4List the points of comparison: coverage, ownership, speed, cost, example, and for topologies, failure impact.
5Apply to the facts given in the case, for example number of branches, budget or need for reliability.
6Reach a clear conclusion or recommendation and link it to security or compliance if the question allows.
7Add a neat labelled diagram only if time allows and it adds clarity.

Quickest way: Size, shape, device: the three-word check

When to use it: Use when you have under five minutes for a short note or a differentiate question.

Size: place the network on the PAN, LAN, MAN, WAN scale and give one Indian example.
Shape: name the topology and write its one big advantage and one big disadvantage.
Device: name the device and the address it reads (MAC for switch, IP for router).
Write three to five crisp points per side in a two-column style list.
Close with one line on why the choice matters for security or cost.

Common mistakes in Computer Network Basics and Types

Calling the internet a LAN or treating every office network as a WAN.
Students link a WAN to any use of the internet.
Fix: Decide by coverage and ownership. One site under one owner is a LAN. Linked sites across cities form a WAN.
Saying a hub and a switch work the same way.
Both connect many devices in a star layout.
Fix: A hub sends data to all ports. A switch learns addresses and sends data only to the target port, which cuts collisions and snooping.
Stating that a star network never fails.
Students remember that one node failing does not affect others.
Fix: Add that failure of the central hub or switch brings down the whole network.
Mixing up a router and a gateway.
Home routers are loosely called gateways.
Fix: A router forwards packets between networks. A gateway translates between different protocols or architectures.
Writing physical topology and logical topology as the same thing.
Textbooks often show only the physical layout.
Fix: Physical topology is the actual cabling layout. Logical topology is how data flows. Mention both if the question is broad.
Giving definitions with no example or application.
Students memorise textbook lines.
Fix: Add one example per point, such as a company head office, branch offices and a data centre.

Worked examples

Example 1

A listed company has its head office in Mumbai, a plant in Pune and branches in Delhi and Chennai. Identify the type of network that connects all sites, and distinguish it from the network inside the Mumbai office.

Show the solution

The sites lie in different cities, so the connecting network covers a large geographic area. This is a WAN.
The network inside the Mumbai office covers one building under one owner. This is a LAN.
Compare: a LAN has a small range, high speed, low cost and private ownership. A WAN has a large range, usually lower speed, higher cost and often uses leased lines or public carriers.
Link to compliance: the WAN crosses public infrastructure, so it needs encryption such as a VPN, while LAN controls focus on access and internal segregation.

Answer: The inter-city network is a WAN and the Mumbai office network is a LAN. A LAN is local, fast and privately owned. A WAN spans cities and needs stronger transmission security.

Example 2

A firm with 5 computers wants a full mesh network. Calculate the number of links and ports per computer, and state one advantage and one disadvantage of this topology.

Show the solution

Number of nodes n = 5.
Links = n(n − 1) ÷ 2 = 5 × 4 ÷ 2 = 10.
Ports per computer = n − 1 = 4.
Advantage: if one link fails, data can use another path, so reliability is high.
Disadvantage: cabling and ports grow quickly, so cost and complexity are high.

Answer: A full mesh of 5 computers needs 10 links and 4 ports on each computer. It is highly reliable but costly and complex.

Exam tips

Prepare a one-page comparison of PAN, LAN, MAN and WAN. This is the most likely differentiate question.
For topologies, always give advantages, disadvantages and the effect of a single failure. Examiners look for all three.
In case-based questions, recommend a topology or network type for the facts given, such as budget, number of sites or need for uptime, and justify it.
Name the address each device uses: MAC for switches and bridges, IP for routers. It shows depth in few words.
Link the answer to security where possible, for example a WAN needs a VPN, a shared bus is easy to tap.

Practice questions from Network Basics and Security

Computer Network Basics and Types: frequently asked questions

What is the difference between LAN, MAN and WAN?

A LAN covers a building or campus. A MAN covers a city. A WAN covers countries or the world. Speed generally falls and cost rises as coverage grows.

Which network topology is most commonly used today?

The star topology is the most common in offices because it is easy to manage and a single node failure does not affect the rest. Its weakness is the central switch, which is a single point of failure.

What is the difference between a switch and a router?

A switch connects devices within one network and forwards data using MAC addresses. A router connects different networks and forwards data using IP addresses.

Do I need to draw diagrams in the CS Professional exam?

The paper is descriptive. A simple labelled diagram can help explain a topology, but clear points and a case-based conclusion earn the marks.