OCR J277 Mark Scheme

OCR	GCSE (9-1) Computer Science Mark Scheme J277/01: Unit 1.3 Network Topologies

Question	Answer	Marks	Guidance
1a	Star Topology	1
1b	Central Device: A central hub or switch is drawn and labelled. (1) Peripherals: At least 5 computers and 1 printer are drawn. (1) Connections: All devices connect only to the central switch (no direct connections between computers). (1)	3	Examiner's Note: Labels are required. If boxes are drawn without labels, cap at 1 mark max. If devices are connected to each other (daisy-chained) or form a ring, 0 marks for connections. Accept "Server" in the middle only if it is acting as the central connection point, but "Switch" is preferred.
1c	Point: Easier to add new devices / Scalable / Cheaper cabling costs. (1) Explanation: ...because you only need one cable to the switch, not to every other computer. (1)	2	Comparison: The question asks for an advantage compared to Mesh. "Cheaper" is valid here because Mesh is famously expensive due to cabling. Reject: "Faster" (Mesh can be faster).
1d	Point: Reliance on the central switch. (1) Explanation: ...if the switch fails, the whole network goes down (Single point of failure). (1)	2	Reject: "If one cable breaks, the network fails" (This is true for Bus/Ring, but false for Star. In Star, only that one device fails).
2a	1 mark: All devices/nodes are connected to... 1 mark: ...every other device (Full) OR multiple other devices (Partial).	2	Key Concept: Decentralised connection. Allow: "A network where devices are interconnected without a central switch."
2b	Point: No single point of failure / Data has multiple routes. (1) Explanation: ...if one cable/device breaks, data can travel via a different path to reach its destination. (1)	2	Examiner's Note: Use of the term "redundancy" or "self-healing" is creditworthy for the explanation. Reject: "It doesn't use a switch" (True, but doesn't explain robustness on its own).
2c	High cost of cabling / hardware. Difficult/complex to install and maintain. Adding a device requires connecting it to every other device.	1	Accept: "Expensive" (valid for wired mesh due to cabling volume).
3a	Full Mesh: Every device is connected to every other device. (1) Partial Mesh: Devices are connected to some other devices (but not all). (1)	2
3b	Range: The nodes (extenders) act as repeaters/relays to extend the signal range. (1) Routing: Data hops from node to node to reach the user. (1) Connection: The user stays connected seamlessly without needing to log in to a new network. (1)	3	Context: This is about Wi-Fi Mesh (e.g. Sonos, Eero). Focus: The signal hopping between nodes is the key benefit here.