Topologies exam questions

17 Edexcel GCSE Computer Science (1CP2) exam-style questions on Topologies (4.1 Networks), 33 marks in all. Answer them on paper or print them, then open the mark schemes and example answers to see how each is marked.

1Multiple choice1 mark

A small office is installing a new network.

Identify the network topology in which every device is connected to a central switch.

[1 mark]

ABus
BFull mesh
CPartial mesh
DStar

Mark scheme

D Star (1)
The only correct answer is D. The correct answer is star. Accept 'star topology'. Do not accept 'switch' or 'hub' alone.
A is not correct because a bus topology connects every device to a single shared backbone cable
B is not correct because a full mesh connects every device directly to every other device
C is not correct because a partial mesh connects some devices directly to each other, not every device to a central switch

Example answers and how they were marked

Full marks1/1

D Star

Why: Correct option (1); a star topology connects every device to a central switch.

No marks0/1

C Partial mesh

Why: A partial mesh does not connect every device to a central switch; no mark.

No marks0/1

B Full mesh

Why: Assumes all topologies connect every device to a central point; a full mesh connects devices directly to each other, so no mark.

2Multiple choice1 mark

A hospital is planning a new network for one of its wards.

Identify the network topology in which all the devices share a single backbone cable.

[1 mark]

ABus
BFull mesh
CPartial mesh
DStar

Mark scheme

A Bus (1)
The only correct answer is A. The correct answer is bus.
B is not correct because in a full mesh every device is connected directly to every other device, so there is no single shared backbone cable
C is not correct because in a partial mesh some devices are connected directly to several other devices, so there is no single shared backbone cable
D is not correct because in a star topology every device is connected to a central switch, not to a shared backbone cable

Example answers and how they were marked

Full marks1/1

A Bus

Why: Correct topology (1); in a bus all the devices share one backbone cable.

No marks0/1

C Partial mesh

Why: A partial mesh connects some devices directly to several others and has no single shared backbone cable; no mark.

No marks0/1

D Star

Why: Misconception that the shared cable is central: a star uses a central switch, with a separate cable to each device, so no mark.

3Multiple choice1 mark

Identify the characteristic of a mesh topology.

[1 mark]

AData can be sent by more than one route.
BAll devices share a single backbone cable.
CEvery device connects to a central switch.
DSignals are absorbed by terminators at each end.

Mark scheme

A Data can be sent by more than one route. (1)
The only correct answer is A. The correct answer is that data can be sent by more than one route (accept equivalent wording, e.g. data can take alternative routes if a link fails).
B is not correct because sharing a single backbone cable is a characteristic of a bus topology
C is not correct because in a mesh devices connect directly to each other, not all to one central switch, which is a star topology
D is not correct because terminators are used at the ends of a bus cable to absorb signals

Example answers and how they were marked

Full marks1/1

A Data can be sent by more than one route.

Why: Correct characteristic (1); mesh nodes provide alternative routes.

No marks0/1

D Signals are absorbed by terminators at each end.

Why: This is a characteristic of a bus topology, not a mesh topology; no mark.

No marks0/1

C Every device connects to a central switch.

Why: This is a star topology; a common misconception that a mesh also uses a central switch.

4Multiple choice1 mark

Identify a disadvantage of a bus topology.

[1 mark]

AAdding a new device requires a cable to the central device.
BThe whole network stops working if the shared cable is broken.
CEach device must connect directly to every other device.
DThe network has no single point of failure.

Mark scheme

B The whole network stops working if the shared cable is broken. (1)
The only correct answer is B. The correct answer is that the whole network stops working if the shared cable is broken.
A is not correct because it describes a star topology, where each device has its own cable running to the central switch
C is not correct because it describes a full mesh topology, where every node is connected directly to every other node
D is not correct because it describes a mesh topology, which has no single point of failure and so is resilient

Example answers and how they were marked

Full marks1/1

B The whole network stops working if the shared cable is broken.

Why: Correct disadvantage (1): all devices share the one backbone cable, so damage to it brings down the whole bus network.

No marks0/1

A Adding a new device requires a cable to the central device.

Why: Near-miss, not credited: this is a feature of a star topology, where every device needs its own cable to the central switch, so it is not a disadvantage of a bus.

No marks0/1

D The network has no single point of failure.

Why: Misconception: a bus network does depend on a single backbone cable, so it does have a single point of failure. No single point of failure is an advantage of a mesh topology, not a bus disadvantage.

5Short recall1 mark

A bus topology uses terminators at each end of the main cable.

State the purpose of terminators in a bus topology.

[1 mark]

Mark scheme

Award one mark for:

Absorb signals (at the ends of the bus cable) / prevent signals reflecting (back along the cable) (1)

Allow 'stop data/signals bouncing back' for prevent signals reflecting

Do not accept 'terminate the cable' / 'close the end of the cable' on its own

Do not accept boost/repeat/strengthen the signal

Example answers and how they were marked

Full marks1/1

To absorb signals so that they do not reflect back along the bus cable.

Why: Absorbing signals and preventing reflection are alternatives within the one creditworthy point (1).

No marks0/1

To terminate the cable at each end.

Why: Near miss: this is rejected by the 'terminate the cable' guidance because it does not say signals are absorbed or prevented from reflecting.

No marks0/1

To make the signal stronger at the end of the cable.

Why: Misconception: terminators absorb signals; they do not boost, repeat or strengthen them.

6Short recall2 marks

A small office installs a network that uses a star topology, with each device connected to a central switch.

Give two advantages of a star topology.

[2 marks]

Mark scheme

Award one mark for any of the following up to a maximum of two marks:

If one cable/device fails, the other devices are not affected (1)
Fast data transfer/high performance because each device has its own cable/connection (1)
Easy to add/remove devices (1)
Fault finding is easier because each device has its own cable (1)
The switch forwards data only to the destination device, so other devices do not receive it (1)

Do not accept disadvantages, such as the whole network going down if the central switch fails

Do not accept fast/faster/reliable/more reliable on their own, without a reason

Example answers and how they were marked

Full marks2/2

Each device has its own cable to the switch, so if one cable fails the other devices are not affected. It is also easy to add another device.

Why: Failure isolation (1) and easy to add devices (1).

Some marks1/2

It is fast because each device has its own connection.

Why: Fast data transfer qualified by own connection (1), but no second advantage.

No marks0/2

If the central switch fails, the whole network goes down.

Why: This is a disadvantage, not an advantage, so no mark.

7Short recall2 marks

Mesh is a type of network topology.

State two characteristics of a mesh topology.

[2 marks]

Mark scheme

Award one mark for any of the following up to a maximum of two marks:

Each node/device has multiple direct connections to other nodes/devices (in a full mesh, every node is connected directly to every other node) (1)
There is no central device/switch (1)
Nodes act as routers/relay data for other nodes / data can take multiple/different routes to its destination / data can still be sent if a connection/node fails (1)
More connections/cables are needed as the number of nodes increases (1)
The network can be expanded without disrupting existing devices (1)

Allow answers that refer to full or partial mesh.

Allow 'more connections/cables are needed' and 'can be expanded' as characteristics (they may be described as advantages or disadvantages).

Do not accept 'more secure' or 'no collisions' without qualification.

Do not accept 'fast' or 'reliable' without qualification.

Do not accept all devices connect to one main cable (this describes a bus topology).

Do not accept it uses a central switch/hub or data is sent through a central hub (this describes a star topology).

Do not accept 'expensive' without qualification (e.g. because more cables/connections are needed).

Example answers and how they were marked

Full marks2/2

Each device is connected to several other devices, and data can be sent along more than one route.

Why: Multiple direct connections (1) and data can take multiple routes (1).

Some marks1/2

There is no central switch.

Why: No central device credited (1), but only one characteristic given.

No marks0/2

Data is sent through a central hub.

Why: Misconception: this describes a star topology, not a mesh topology.

8Short recall2 marks

Networks can use different topologies.

Define the term network topology.

[2 marks]

Mark scheme

Award one mark for any of the following up to a maximum of two marks:

The layout/arrangement/structure of a network (1)
How devices/nodes are connected together (1)

Allow 'the physical or logical layout/arrangement of a network' for the first point.

Allow 'the way parts of a system/network are connected' for the second point.

Do not award the first mark for 'how devices are connected' on its own.

Do not accept a named topology (e.g. star, bus, mesh) on its own.

Do not accept a network device or how data is transmitted on its own.

Example answers and how they were marked

Full marks2/2

The layout of a network and how the devices in it are connected together.

Why: Layout/arrangement of a network (1) and how devices/nodes are connected together (1).

Some marks1/2

The way devices are connected in a network.

Why: How devices/nodes are connected together (1), but no reference to the layout/arrangement/structure of the network.

No marks0/2

A star network.

Why: Near miss: names a topology but does not define the term.

9Describe2 marks

A school's library uses a star topology for its computers.

Describe the purpose of the central switch in the library's star topology.

[2 marks]

Mark scheme

Award up to two marks for a linked description such as:

The switch receives the data/a packet from the sending device (1) and forwards it only to the destination device (1)
Acts as a central connection point for the devices (1) so any device can send data to any other device on the network (1)
Sends data to the correct device (1) so the other devices on the network do not receive it (1)

For the central device, accept 'switch'. Do not accept 'server'.

Do not accept 'hub' where the response says data is sent only to the destination device (a hub sends data to every device).

Do not accept 'it connects the network to the internet'.

Award a maximum of one mark where a point is made without a linked development.

Example answers and how they were marked

Full marks2/2

The switch receives the data from the computer that is sending it and forwards it only to the device it is meant for, so the other computers do not receive it.

Why: Point (1) for receiving the data and linked development (1) for forwarding it only to the destination device.

Some marks1/2

The switch is the central device that all the computers in the library connect to.

Why: Point (1) for acting as the central connection point, with no linked development, so the maximum of one mark applies.

No marks0/2

The switch connects the library network to the internet so the computers can go on websites.

Why: No creditworthy point; this is the 'connects the network to the internet' response named in the do-not-accept line.

10Describe2 marks

A bus topology uses one main cable that every device connects to.

Describe why data collisions can happen on a bus network.

[2 marks]

Mark scheme

Award up to two marks for a linked description such as:

All devices share a single cable/backbone (1) so if two devices transmit at the same time their signals collide (1)
Signals travel in both directions along the cable (1) so data from different devices can meet/interfere with each other (1)
Only one device can transmit at a time (1) so devices must wait until the cable is free before sending (1)
The more devices that are added to the network (1) the more often collisions happen/the slower the network becomes (1)

Allow 'the data is corrupted and has to be resent' as the linked development of a collision.

Do not accept responses about a broken/missing cable or faulty terminators, as the whole network failing is a different issue.

Do not award 'the data is lost forever' as a result of a collision.

Example answers and how they were marked

Full marks2/2

All the devices share the same cable, so if two devices send data at the same time the signals collide and the data is corrupted.

Why: Point (1) for the shared cable and linked development (1) for two signals colliding.

Some marks1/2

Only one device can send data at a time on a bus network.

Why: Point (1) for one device transmitting at a time, but no development of devices having to wait for the cable to be free.

No marks0/2

The data collides because the terminators are missing from the end of the cable.

Why: No creditworthy point; faulty terminators are excluded by the do-not-accept line.

11Describe2 marks

A mesh topology is used for the sensors in a warehouse.

Describe how a mesh topology keeps working when one of its connections fails.

[2 marks]

Mark scheme

Award up to two marks for a linked description such as:

Each device/node is connected to more than one other device (1) so there is another route for the data to take (1)
Data can be sent along a different path (1) to bypass the failed connection (1)
There is no central device/switch to fail (1) so data can still be passed between the remaining devices (1)

Allow 'sensor' or 'node' for device.

Do not accept 'the failed connection repairs itself' or 'the data is stored until the connection works again'.

Do not accept responses that say a central switch sends the data by another route, as a mesh has no central device.

Do not award generic statements such as 'a mesh is reliable/resilient' without a description of how the data still reaches its destination.

Do not award descriptions of a bus or star network failing.

Accept a reference to a device failing only where the candidate also states that other connections/routes remain available.

Example answers and how they were marked

Full marks2/2

Each sensor is connected to several other sensors, so if one connection fails there is another route for the data to take.

Why: Point (1) for each device being connected to more than one other device and linked development (1) for the alternative route this gives the data.

Some marks1/2

If a connection fails the data is sent along a different path.

Why: Point (1) for sending data along a different path, but no development of how this bypasses the failed connection, so the second mark is not earned.

No marks0/2

If a connection fails, the central switch sends the data by another route, so a mesh is reliable.

Why: No creditworthy point; a mesh has no central device, and both the central switch response and the generic 'reliable' statement are excluded by the do-not-accept lines.

12Describe2 marks

In a bus topology, data is sent along the main cable as signals. The cable has a terminator at each end.

Describe the purpose of the terminators in a bus topology.

[2 marks]

Mark scheme

Award up to two marks for a linked description such as:

Absorb the signal at the ends of the cable (1) so that it does not reflect/bounce back along the cable (1)
Stop the signal reflecting/bouncing back (1) so it does not interfere with data being sent on the cable (1)
Stop the signal reflecting/bouncing back (1) which would cause data corruption/collisions on the cable (1)

Do not accept 'they terminate the network' or 'they stop the signal escaping' without development of what this prevents.

Do not accept 'so the data is not lost'/'stops data being lost' on its own, as it does not describe reflection.

Do not award 'they join the two ends of the cable together'.

Example answers and how they were marked

Full marks2/2

The terminators absorb the signal when it reaches the end of the cable so that it does not reflect back along the cable.

Why: Point (1) for absorbing the signal at the end of the cable and linked development (1) for stopping it reflecting back.

Some marks1/2

The terminators absorb the signal at the ends of the main cable.

Why: Point (1) for absorbing the signal, but no development of what this prevents.

No marks0/2

The terminators stop the signal escaping from the end of the cable so the data is not lost.

Why: No creditworthy point; 'stops the signal escaping' and 'so the data is not lost' without any description of reflection are named in the do-not-accept lines.

13Explain2 marks

A bus topology has a terminator at each end of its cable.

Explain why terminators are needed in a bus topology.

[2 marks]

Mark scheme

Award up to two marks for a linked explanation such as:

Terminators absorb the signal at the ends of the cable (1) so it is not reflected back along the bus (1)
Terminators prevent signals reflecting/bouncing back (1) so the reflected signal does not corrupt data on the cable (1)
Terminators absorb the signal (1) so it does not collide/interfere with data being sent by other devices (1)
Terminators stop the signal reflecting back down the cable (1) so data can be transmitted and received without errors (1)

For both marks, the expansion must follow/associate with the statement.

Allow 'interfere'/'corrupt' only where the answer says the reflected signal mixes with/collides with data on the cable.

Do not accept 'to stop the signal' on its own, as stopping the signal is not the same as stopping it reflecting back along the cable.

Do not accept 'to terminate the cable/network', 'to end the cable' or 'to stop the cable breaking'.

Do not award responses that only repeat the stem, e.g. 'because there is a terminator at each end'.

Example answers and how they were marked

Full marks2/2

Terminators absorb the signal at each end of the cable (1) so that it does not reflect back along the bus (1).

Why: Linked point (1) and reason (1): absorbing the signal is linked to it not being reflected back along the bus.

Some marks1/2

Terminators absorb the signal at the ends of the cable.

Why: Awarded 1 mark for the point that the signal is absorbed, but no linked consequence is given.

No marks0/2

They terminate the network so the cable does not break.

Why: No credit: it does not say the signal is absorbed or that reflections are prevented, and the mark scheme rejects 'to terminate the network' and 'to stop the cable breaking'.

14Explain2 marks

A small office uses a star topology with a central switch.

Explain one benefit of using a star topology in the office.

[2 marks]

Mark scheme

Award up to two marks for a linked explanation such as:

If one cable/device fails, the other devices on the network are not affected (1) because each device has its own separate connection to the central switch (1)
Faults are easier to find (1) because each device has its own cable, so the faulty cable can be checked on its own (1)
Data is sent only to the intended device (1) because the central switch forwards the data only to the device it is addressed to (1)
Data transfer is fast (1) because each device has its own cable, so devices do not share the cable with each other (1)
New devices can be added easily (1) because a device only needs one cable to a spare port on the central switch (1)

For both marks, the expansion must follow/associate with the statement.

A benefit stated on its own can earn one mark; the second mark is only for a linked reason.

Accept 'switch' for the central device.

Do not accept 'server' or 'hub' for the central device.

Do not accept 'hub', as a hub sends data to all devices, not only to the intended device.

Do not award a mark for responses that say only that the network is better/more reliable/easier without naming a benefit.

Example answers and how they were marked

Full marks2/2

If one of the cables breaks, the other devices can still communicate because each device has its own separate cable connected to the central switch.

Why: Linked benefit (1) and reason (1): a single cable failure does not affect the other devices because each device has a separate connection to the switch.

Some marks1/2

If one cable breaks, the other devices are not affected.

Why: A benefit is stated on its own (1), but there is no linked reason about each device having its own connection to the central switch, so the second mark is not awarded.

No marks0/2

It is better than a bus topology because every device connects to the central server.

Why: No credit: 'better' does not name a benefit, so no first mark, and 'server' is not accepted as the central device, so there is no linked reason either.

15Explain2 marks

A mesh topology has many connections between devices.

Explain one reason why a mesh topology is resilient.

[2 marks]

Mark scheme

Award up to two marks for a linked explanation such as:

There is no single point of failure (1) because there is no central device that all the other devices depend on (1)
If one device/connection fails, the network can still communicate/work (1) because data can be sent along another route between devices (1)
A faulty device/connection can be bypassed (1) because each device is connected to more than one other device (1)

For both marks, the expansion must follow/associate with the statement.

Allow one mark for a correct point without a linked reason.

Allow 'the network can still communicate/work' as the outcome point and 'if one cable/connection breaks' as the failure point.

Allow 'reliable'/'robust' only when expanded with a reason, such as multiple routes or no single point of failure.

Do not accept 'it has many connections' on its own without saying why this makes the network resilient.

Do not accept 'mesh is faster' or 'data is backed up' as these do not explain resilience.

Do not accept 'it uses a central switch/device' as part of the explanation.

Example answers and how they were marked

Full marks2/2

There is no single point of failure (1) because each device is connected to several others, so data can take another route if one connection fails (1).

Why: Linked point (1) and reason (1): no single point of failure is explained by multiple connections and alternative routes.

Some marks1/2

If one device fails, the network still works.

Why: Awarded 1 mark for the correct outcome point; no linked reason about multiple routes or connections is given.

No marks0/2

It is resilient because a central switch redirects data around a broken cable.

Why: No credit: the mark scheme does not accept a central switch in a mesh explanation, and no valid point about multiple routes is given.

16Explain2 marks

A bus topology uses one main cable shared by all devices.

Explain why a bus topology can be a security risk.

[2 marks]

Mark scheme

Award up to two marks for a linked explanation such as:

All devices receive every data packet (1) because the main cable is shared by all nodes (1)
Data can be read by any device on the network (1) because there is no central switch to send it only to the destination (1)
A device can intercept/capture data not meant for it (1) because all transmissions travel along the same cable (1)
Any device can view all data on the cable (1) so data is not private/secure (1)

For both marks, the expansion must follow/associate with the statement.

Do not accept 'it is easy to hack' without saying data can be seen/intercepted on the shared cable.

Do not accept 'the central switch can be hacked' because a bus topology has no central switch.

Example answers and how they were marked

Full marks2/2

Any device on the bus can see all the data (1) because every packet travels along the same shared cable (1).

Why: Linked point (1) and reason (1): data is visible to all devices because the cable is shared.

Some marks1/2

All devices can see the data.

Why: Awarded 1 mark for stating that all devices can see the data, but no linked reason about the shared cable is given.

No marks0/2

It is less secure because the central switch can be hacked.

Why: No credit: a bus topology has no central switch; the answer gives a misconception and no valid point about the shared cable.

17Discuss6 marks

A primary school is building a new computer room with 15 computers and one shared printer. The school wants a reliable network that is easy to manage.

Discuss the characteristics of a star topology for the school's computer room.

Your answer should consider:

the role of the central device
the benefits of this topology for the school
the drawbacks of this topology for the school.

[6 marks]

Mark scheme

Indicative content

The role of the central device

All computers and the printer connect separately to a central switch.
The central device receives a packet from the sending device and forwards it only to the destination device.
Each device has its own cable to the central switch, or a wireless connection to a central access point.

Benefits

If one computer's cable or connection fails, the other computers are not affected, so the school's network stays available.
Data transfer is fast because each device has a dedicated connection and data is sent directly to the destination.
It is easy to add a new computer by connecting it to a free port on the central switch.
It is easy to manage and find faults because each device has its own connection to the central switch.

Drawbacks

If the central switch fails, the whole network goes down.
More cable is needed than in a bus topology because every device needs its own cable to the central switch.
The number of devices is limited by the number of ports on the central switch.
The central switch and the extra cabling add cost to the school's network.

Levels

Level 0 (0 marks): No rewardable content.
Level 1 (1–2 marks): Basic, independent points are made, showing elements of understanding of key concepts/principles of computer science. (AO1) The discussion will contain basic information with little linkage between points made or application to the context. (AO2)
Level 2 (3–4 marks): Demonstrates adequate understanding of key concepts/principles of computer science. (AO1) The discussion shows some linkages and lines of reasoning with some structure and application to the context. (AO2)
Level 3 (5–6 marks): Demonstrates comprehensive understanding of key concepts/principles of computer science to support the discussion being presented. (AO1) The discussion is well developed, with sustained lines of reasoning that are coherent and logically structured, and which clearly apply to the context. (AO2)

Level 3 responses must cover the role of the central device and at least one benefit and one drawback applied to the school.

Do not accept 'server' as the central device; accept switch, hub or wireless access point.

Example answers and how they were marked

Full marks6/6

In a star topology each computer and the printer has its own cable to a central switch. The switch receives a packet and sends it only to the destination computer, so data transfer is fast. If one computer's cable fails, the other computers are not affected, which keeps the school's network reliable. It is easy to add a new computer by plugging it into a free port on the switch. However, if the central switch fails, the whole network goes down. More cable is needed than in a bus topology, and the number of computers is limited by the number of ports on the switch.

Why: Level 3: comprehensive and applied to the school. Covers the central switch forwarding data, fast transfer, cable failure isolation, easy expansion, central switch failure and port limits.

Some marks4/6

All the computers connect to a central switch. If one cable breaks, the other computers still work. But if the switch breaks, the whole network stops.

Why: Level 2: adequate with some linkage. Gives the central device, one benefit and one drawback, but does not develop fast data transfer, ports or cabling cost.

Some marks1/6

Every computer connects to a central switch. If one computer breaks, the whole network stops working because all data goes through the switch.

Why: Level 1: one basic correct point about each computer connecting to a central switch. The second sentence wrongly says a single computer failure brings down the whole network.

Revise Topologies first

Keep practising Topologies

More exam questions on 4.1 Networks