Network Structure

Introduction

Networks are classified by their geographic scale — how far apart the connected devices actually are. The same underlying ideas (protocols, media, devices) apply at every scale, but the name changes with the distance covered.

Concept

• PAN (Personal Area Network) — the smallest scale, covering just a few metres around one person, typically using Bluetooth (connecting a phone to wireless earbuds, for example).
• LAN (Local Area Network) — confined to one building or campus, like a school's computer lab or an office floor.
• MAN (Metropolitan Area Network) — spans a city, connecting multiple LANs across it. Cable TV networks within a city are a standard example.
• WAN (Wide Area Network) — spans across cities, countries, or continents — offices in Mumbai and Delhi connected together is a WAN. The Internet itself is the largest possible WAN.

Explanation

The four types form a strict scale: PAN < LAN < MAN < WAN. Most exam questions describe a real scenario (a scale of distance, or a real example like cable TV) and expect you to identify which category it falls into, rather than asking for definitions directly.

Note: The clearest signal in a question is distance: "within one building" → LAN, "within one city" → MAN, "between cities/countries" → WAN.

Summary

Networks are classified by geographic scale: PAN (a few metres, e.g. Bluetooth), LAN (one building), MAN (one city), WAN (across cities or countries, with the Internet as the largest example).

Introduction

Beyond scale, a network also has a topology — the physical or logical layout of how its devices are connected to one another. The shape you choose affects cost, reliability, and how easy the network is to troubleshoot.

Concept

• Bus Topology — every device connects to one single central cable, called the "backbone". Simple and uses the least cable, but if the backbone cable fails, the entire network goes down, and it can be hard to isolate which device is causing a fault.
• Star Topology — every device connects individually to one central point (a Hub or Switch). If one device's cable fails, only that device is affected — the rest of the network keeps working. This is the standard layout in modern networks.
• Ring Topology — devices are connected in a closed loop, each one connected to exactly two neighbours, with data passing around the ring.
• Mesh Topology — every device connects directly to every other device — highly reliable (many alternate paths if one link fails) but expensive, since the amount of cabling grows very quickly as devices are added.
• Tree Topology — several Star networks connected together through their central hubs, arranged like a hierarchy with a main "root" hub at the top. Combines Star's easy fault isolation with the ability to grow a much larger network, but a failure in a higher-level hub takes down every branch below it.

Explanation

Star Topology's one real weakness is the flip side of its strength: since every device depends on the central Hub/Switch, if that central device fails, the entire network goes down at once — even though no individual cable failure would.

Tip: "Fault detection is easier" and "one node failing doesn't affect the others" are the two phrases that point directly to Star Topology in an exam question — they're its two headline advantages over Bus.

Summary

Bus (one shared backbone, single point of failure), Star (central hub, easiest fault isolation, but the hub itself is a single point of failure), Ring (closed loop), Mesh (every device connected to every other, reliable but expensive), and Tree (Star networks combined into a hierarchy) are the standard network topologies.

You need to know the specific Pros and Cons of each for the exam.

Bus vs. Star Topology