Network types, topologies and switching
Networks are grouped by size (LAN, MAN, WAN), drawn by topology (bus, star, ring, mesh) and move data by circuit, message or packet switching.
Network types by area
| Type | Area covered | Example |
|---|---|---|
| PAN (personal area network) | A few metres around one person | Phone linked to earbuds by Bluetooth |
| LAN (local area network) | One building or campus | An office or university network |
| MAN (metropolitan area network) | A city | A firm's offices linked across Colombo |
| WAN (wide area network) | A country or the world | A bank's branch network across the island; the internet |
Network topologies
| Topology | Layout | Advantages | Disadvantages |
|---|---|---|---|
| Bus | All devices joined to one main cable (backbone) | Cheap; little cable | One break in the backbone stops the network; slows as traffic grows; faults hard to find |
| Star | Every device joined to a central switch or hub | Easy to add devices; a cable fault affects only one device | If the central device fails, all stop; more cable |
| Ring | Each device joined to two others in a closed loop; data goes round | Orderly flow, no data collisions | One break can stop the ring; adding devices disturbs it |
| Mesh | Devices joined to many or all others | Many paths, so very reliable | Costly; a lot of cabling |
| Tree / hybrid | Star networks joined in levels, or a mix of layouts | Easy to expand; suits large firms | Depends on the main backbone |
Counting links in a full mesh
How many direct links are needed to join 5 branch offices in a full mesh?
- Each office links to every other office: links = n(n − 1) ÷ 2
- = 5 × 4 ÷ 2
- = 20 ÷ 2 = 10
10 links. A star with one central switch would need only 5.
Switching types
| Type | How it works | Example | Note |
|---|---|---|---|
| Circuit switching | A dedicated path is set up for the whole session | Traditional telephone call | Path stays reserved even when no one speaks |
| Message switching | The whole message is stored at each node, then passed on (store and forward) | Early telegram and email systems | Delays at each node |
| Packet switching | Data is split into small numbered packets that may take different routes and are put back in order | The internet, email, web pages | Shares lines efficiently; most used today |
Packet switching
A Sri Lankan bank uses LANs inside each building and a WAN to link its branches across the island, so a deposit made in Jaffna can be seen at once in Matara; traffic over the internet travels by packet switching.
Short answer: “What is a LAN?” A local area network: computers linked within one building or campus, such as an office.
Structured question: “Distinguish between circuit switching and packet switching.” Circuit switching reserves one dedicated path for the whole session (phone call). Packet switching splits data into packets that share lines and may take different routes (internet).
Essay: “Explain the main network topologies with diagrams, giving their advantages and disadvantages.” Define topology, draw and explain bus, star, ring, mesh and hybrid, with one advantage and one disadvantage each.
Sizes: P-L-M-W (Personal, Local, Metropolitan, Wide). Topologies: 'Big Stars Rarely Meet' = Bus, Star, Ring, Mesh.