Networking: Devices, Topologies & Protocols
🔒 Log in to trackNetwork types and topologies
🔒 Log in to trackBy reach:
| Type | Span | Example |
|---|---|---|
| PAN (Personal) | ~10 m around one person | Bluetooth headset link |
| LAN (Local) | Building/campus; Ethernet/Wi-Fi; privately owned | Office/lab network |
| MAN (Metropolitan) | City | Cable TV/city ISP network |
| WAN (Wide) | Countries/continents; leased lines | The Internet is the largest WAN |
A VPN builds an encrypted private tunnel over a public network. Networks run as client-server (dedicated servers) or peer-to-peer (equal machines).
Topologies (physical layout):
| Topology | Structure | Notes |
|---|---|---|
| Bus | One backbone cable with terminators | Cheap; backbone failure kills all; collisions |
| Star | All nodes wired to a central hub/switch | Most common (modern Ethernet); one cable failure is local, but the hub/switch is a single point of failure |
| Ring | Each node joined to exactly two neighbours | Token passing; one break can halt the loop |
| Mesh | Every pair of nodes directly linked | Most reliable, costliest; full-mesh links = n(n-1)/2 |
| Tree | Hierarchy of stars | Used in large LANs |
| Hybrid | Mix of the above | Real-world networks |
Wireless: Wi-Fi = IEEE 802.11 family (n/ac/ax = Wi-Fi 4/5/6); Bluetooth = 802.15, ~10 m PAN; infrared needs line of sight.
Detailed notes
Networks by their reach
| Type | Span | Everyday example |
|---|---|---|
| PAN (Personal Area Network) | ~10 metres around one person | Bluetooth headset with a phone |
| LAN (Local Area Network) | one building or campus | school computer lab, office floor |
| MAN (Metropolitan Area Network) | one city | city cable network |
| WAN (Wide Area Network) | country or the world | the Internet is the largest WAN |
LANs are privately owned and fast; WANs use leased/telecom links over long distances. The span ladder PAN < LAN < MAN < WAN answers most identification questions.
Topologies — the shape of the wiring
A topology is how computers are arranged and connected.
| Topology | Layout | Strength | Weakness |
|---|---|---|---|
| Bus | all nodes tap into ONE backbone cable with terminators at both ends | cheapest, least cable | backbone break kills the whole network; collisions |
| Ring | each node joins exactly two neighbours, forming a circle | orderly token passing | one broken node/link can break the ring |
| Star | every node connects to a central device (hub/switch) | one cable failure hurts only one node; easy to extend | the central device is the single point of failure |
| Mesh | every node connects to every other node | most reliable, no traffic jams | most cables, costliest |
| Tree (hierarchical) | star networks joined on a bus | scalable for big campuses | root failure splits the tree |
Star is the shape used in modern offices — switches sit at the centre. Mesh is the most fault-tolerant.
Mesh arithmetic — the one formula
In a full mesh of n computers, every computer connects to the other n-1 computers, so each of the n nodes has n-1 lines; counting every line twice (A-B and B-A) gives:
links = n x (n-1) / 2
For n = 4: 4x3/2 = 6 links. For n = 5: 10. For n = 6: 15. This is the classic numeric question of the topic — halve the product, never use n squared.
Standards that name the wires
- Ethernet (wired LAN) = IEEE 802.3; Wi-Fi (wireless LAN) = IEEE 802.11; Bluetooth = IEEE 802.15.
- Trap: calling Wi-Fi "802.3" — 802.3 is the wired Ethernet standard.
Quick revision
- PAN (10 m) < LAN (building) < MAN (city) < WAN (country/world); Internet = biggest WAN.
- Bus = one backbone; Ring = circle of neighbours; Star = central hub/switch; Mesh = all-to-all.
- Mesh links = n(n-1)/2 (6 computers = 15 links).
- Star's weakness = central device; Bus's weakness = backbone break.
- Ethernet 802.3, Wi-Fi 802.11, Bluetooth 802.15.
Types of questions asked
Every way this subtopic shows up in exams — how to recognise it, the formula or logic to use, and a solved example.
Type 1: Network type by spanvery common4 practice Q
A situation is described (school lab, city cable, worldwide web, one person's Bluetooth) and PAN/LAN/MAN/WAN is asked — or 'the Internet is the largest ___'.
- Line up the ladder: PAN (~10 m, one person) < LAN (building/campus) < MAN (city) < WAN (country/world).
- Match the situation's span, not its technology.
- Standard facts: Internet = largest WAN; school lab = LAN; Bluetooth headset = PAN.
Example: A computer lab of one school connected by a switch forms a —
LAN (Local Area Network) — a single-building privately owned network.
Type 2: Topology identification by descriptionvery common4 practice Q
The layout is described (every node to a central device; every node to every other; a single backbone; a circle) and the topology is asked.
- Central device with all nodes hanging off = Star.
- Every node linked to every other = Mesh.
- One shared backbone cable with terminators = Bus; closed circle of neighbours = Ring; stars joined on a backbone = Tree.
Example: In which topology is every computer connected to a central hub or switch?
Star topology — one cable break isolates only that node, but the central device is the single point of failure.
Type 3: Mesh link count (numeric)common3 practice Q
'How many links are needed for a full mesh of n computers?' — pure arithmetic on n(n-1)/2.
- Use links = n x (n-1) / 2 — every node talks to the other n-1, and each line would be counted twice.
- Never use n squared; halve the product.
- Check: n = 4 gives 6, n = 5 gives 10, n = 6 gives 15.
Example: How many cable links are needed for a full mesh of 6 computers?
6 x 5 / 2 = 15 links.
Type 4: Topology strengths and failure pointscommon3 practice Q
A statement about which topology is cheapest, most reliable, has a single point of failure, or what happens when a cable breaks.
- Star: one cable break = one node only; central hub/switch failure = whole network down.
- Bus: backbone break = total failure; cheapest.
- Mesh: most reliable, most cable (costliest).
- Ring: one broken node/link can stop the ring (token passing).
Example: In a star topology, failure of the central hub results in —
The whole network stops communicating — every node depends on the hub; the individual cables are irrelevant.
Type 5: IEEE standards and LAN jargonoccasional2 practice Q
'Wi-Fi is IEEE ___' or 'Ethernet works on which standard' — matching 802.x numbers to technologies.
- Ethernet (wired) = IEEE 802.3; Wi-Fi (wireless) = IEEE 802.11; Bluetooth = 802.15.
- The recurring trap: pairing Wi-Fi with 802.3.
- LAN = Ethernet/Wi-Fi family; the Internet = a WAN built of many networks.
Example: Wi-Fi networks are standardised under IEEE —
802.11 — 802.3 is wired Ethernet, 802.15 is Bluetooth.
Shortcut tricks
⚡ Mesh half-row sum
Full-mesh links for n nodes = n(n-1)/2: 6 nodes -> 6x5/2 = 15. Half of n rows of (n-1) - compute, don't memorise per-n.
Example: How many links in a full mesh of 8 computers?
8x7/2 = 28.
⚡ PLMW span ladder
PAN < LAN < MAN < WAN - Personal, Local, Metropolitan, Wide. The Internet is the WAN of WANs.
Example: A network limited to one office building is a?
LAN.
⚡ Star = spine
Modern offices run star topology around a switch. If a question says 'central device fails, whole network down', it is describing star's weakness.
Example: In which topology is the central hub a single point of failure?
Star.
Where students lose marks
Using the bus topology's weaknesses for star questions.
Counting mesh links as n^2 - duplicates don't count; it's n(n-1)/2.
Calling Wi-Fi 'IEEE 802.3' - 802.3 is wired Ethernet; Wi-Fi is 802.11.
Practice sets — 20 questions
Sets of 10, mixed across the question types above. Each answer comes with a step-by-step explanation.
Topic test · 10 questions
Suggested time 5 min · wrong answers go to your mistake notebook automatically.