Star and mesh topologies – GCSE Computer Science exam questions with mark scheme

1Grade 4–54 marks

The diagram shows the network in a small dental surgery.

(a) Identify the network topology shown. [1]

(b) Give two advantages of this topology. [2]

(a) Star(1)
(b) Any two from: if one cable / device fails, the rest of the network is unaffected; easy to add new devices (just connect to the switch); good performance / fewer data collisions as the switch sends data only to the device it is addressed to; easy to find / isolate faults. Ignore 'faster' with no reason(1)
(b) Second advantage from the list (different point)(1)
(c) If the central switch fails, the whole network stops working (single point of failure); allow: needs a lot of cable, so can be expensive to install(1)
Answer: (a) Star (b) e.g. one failed cable doesn't affect others; easy to add devices (c) Switch failure stops the whole network
Examiner tip: Don't say 'it is fast' alone – explain why (the switch only sends data to the device it is meant for).

2Grade 8–96 marks

The diagram shows six routers, A to F, in a fully connected mesh network.

(a) The number of connections needed in a full mesh is n(n − 1) ÷ 2, where n is the number of devices. Calculate the number of connections needed for the six routers. [1]

(b) Explain one reason why a mesh topology is used for routers on the internet. [1]

(c) A user types www.example-shop.co.uk into a web browser. Describe how the Domain Name System (DNS) is used to find the web server. [4]

(a) 15 (6 × 5 ÷ 2)(1)
(b) There are many routes between devices, so if one connection / router fails data can be sent another way (more reliable / no single point of failure)(1)
(c) The browser / device sends the domain name / URL to a DNS (resolver) server; allow: first checks its own cache(1)
(c) The DNS server looks up / searches its database / records for the domain name to find the matching IP address(1)
(c) If it does not have a record, the request is passed to another (higher-level / authoritative) DNS server(1)
(c) The IP address is returned to the browser, which uses it to send a request to / connect to the web server; do not accept 'the DNS server sends the web page'(1)
Answer: (a) 15 (b) Multiple routes so data can be rerouted if a link fails (c) Domain name sent to DNS server → looked up → passed on if not found → IP returned and used to contact web server
Examiner tip: DNS returns an IP address – it does not send the web page itself. Saying 'DNS finds the website' scores nothing.

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