Bus, ring and mesh topologies

The layout of a network: bus shares one cable, ring passes data around a loop, and mesh links devices by many paths.

Part of: WA Computer Science ATAR Year 11 — Network Communications — Module 83

Understanding Bus, ring and mesh topologies in WA Computer Science ATAR Unit 1

What it does: Full mesh means each device has a direct link to all others, so data can reroute if one link fails. Partial mesh keeps extra paths between key devices but skips some links, reducing cabling cost compared with full mesh. A bus topology uses a single shared cable (the bus). A central switch with a cable per device describes a star topology. In a basic ring, data has only one path around the loop, so one failed device or cable can stop the whole network. Redundant routing would offer another path. Mesh is the most fault tolerant of the three because of redundant paths, though it costs more to install.

Common mistakes: In a bus topology the single shared cable is the single point of failure. One failed device does not stop the others. The line should read: weak point: the one cable. In a ring, data is passed from each device to the next device around the loop. There is no central hub. The line should read: data passes to next device.

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This module's key terms are also in a printable crossword (Modules 315–470) and word search (Modules 100–470).

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Learning

Duo

In a bus topology, how do the devices connect?

Each device has its own cable to a central switchThey all share one main cable

Matches

Bus topology: if one cable breaks, only that device is affected

↓

The shared backbone cable is a single point of failure, so a break can cut off many or all devices, not just one

Applying

Meanings

Term

topology

Meaning

The layout of a network: bus shares one cable, ring passes data around a loop, and mesh links devices by many paths.

Practice

BUS: PC1, PC2, PC3 share one cable

Testing

Gaps

busCables =

Check Answer

Spots

2all devices share one cable

3weak point: any one device

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Quick Questions

1. In a bus topology, how do the devices connect?

A. Each device has its own cable to a central switch

B. They all share one main cable ✓

A bus topology uses a single shared cable (the bus). A central switch with a cable per device describes a star topology.

2. In a ring topology, how does data travel?

A. Straight from the sender to every other device at once

B. Around a loop from device to device ✓

In a ring, each device passes data to the next one around the loop until it reaches its destination.

3. Which topology is the most likely to stop working completely if its one main cable breaks?

A. Bus ✓

B. Full mesh

A bus relies on a single shared cable, so a break in it is a single point of failure. A full mesh has many alternative paths.

4. Which statement describes a full mesh?

A. Every device is linked directly to every other device ✓

B. Only some devices are linked directly to each other

In a full mesh every device has a direct link to all the others. Only some links existing is a partial mesh.

5. Which is a disadvantage of a full mesh topology?

A. It needs many cables and connections, so it is expensive ✓

B. It has a single point of failure on the main cable

The number of links grows quickly as devices are added, so full mesh is costly. Its many paths mean it has no single point of failure.

Match the Pairs

bus topology → All devices share one main cable, so a break in that cable can stop the whole network

ring topology → Each device connects to two neighbours and data travels around a closed loop

A full mesh links every device directly to every other device, giving many alternative paths → full mesh topology

A partial mesh links only some devices by multiple paths, which costs less than a full mesh → partial mesh topology

Bus topology: if one cable breaks, only that device is affected → The shared backbone cable is a single point of failure, so a break can cut off many or all devices, not just one

Mesh topology: has a single point of failure, so it is the least reliable layout → Mesh has many paths between devices, so data can be rerouted and it avoids a single point of failure

Key Term

topology

The layout of a network: bus shares one cable, ring passes data around a loop, and mesh links devices by many paths.

Fill in the Blanks

1. busCables = 1

Hint: Type how many cables all devices share in a bus topology.

2. if cableOk == False: print("Bus down")

Hint: Type the Boolean value that means the single shared cable has failed, taking the whole bus network down.

3. nextDevice = (i + 1) % n

Hint: Type the operator that wraps the last device in the ring back round to the first.

4. fullLinks = n * (n - 1) / 2

Hint: Type the number each device subtracts, because it does not link to itself in a full mesh.

5. partialMesh = links < fullLinks

Hint: Type the comparison operator showing a partial mesh has fewer links than a full mesh.

Spot the Error

Question 1

A topology = bus

B all devices share one cable

C weak point: any one device

Line C — In a bus topology the single shared cable is the single point of failure. One failed device does not stop the others. The line should read: weak point: the one cable.

Question 2

A topology = ring

B devices form a loop

C data goes via a central hub

D one break can stop the ring

Line C — In a ring, data is passed from each device to the next device around the loop. There is no central hub. The line should read: data passes to next device.

Question 3

A topology = mesh

B links = one shared cable

C if one link fails, reroute

Line B — A mesh links devices by many paths. One shared cable describes a bus. The line should read: links = many paths.

Question 4

A n = 5

B full_mesh_links = n*(n-1)/2

C partial mesh uses fewer links

D full mesh for 5 devices = 20

Line D — A full mesh of 5 devices needs 5*4/2 = 10 links, not 20. The line should read: full mesh for 5 devices = 10.

Question 5

A topology = bus

B advantage: cheap to install

C disadvantage: needs most cable

Line C — A bus uses little cable, which is its advantage. Its disadvantage is that collisions increase as more devices share the cable. Needing the most cable describes a full mesh. The line should read: disadvantage: collisions grow.

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