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Standards and common protocols

OCR GCSE Computer Science (J277) · Computer systems (Paper 1) › Networks, connections and protocols › Wired and wireless networks, protocols and layers

Practise Standards and common protocols. 11 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.

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Quick recall

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State what the letters HTTPS stand for.
HyperText Transfer Protocol Secure

Sample questions

Written for this site in the style of OCR exam questions. They are not taken from real past papers.

Question 1Easy3 marks
(a) State what is meant by a protocol.[1]
(b) Which protocol is used to send an email?
Tick (✓) one box.[1]
  • POP
  • SMTP
  • IMAP
  • FTP
(c) State what the letters HTTPS stand for.[1]
Show the answer and mark scheme
(a)
  • a set of rules for how data is transferred / how devices communicate
(b) Answer: SMTP
(c) Answer: HyperText Transfer Protocol Secure
  • HyperText Transfer Protocol Secure
Question 2Medium4 marks
(a) Explain the difference between HTTP and HTTPS.[2]
(b) Give one example of a website where it is essential to use HTTPS. Explain why.[2]
Show the answer and mark scheme
(a)
  • HTTPS encrypts the data sent between the browser and the web server (HTTP does not)
  • so if the data is intercepted it cannot be understood
(b)
  • online banking / online shopping / any login page
  • because sensitive data, e.g. passwords or card details, is sent
Question 3Hard5 marks
A student uploads a 50 MB video to a video-sharing website. The video is sent across the Internet using the TCP/IP protocols.
(a) Explain why TCP splits the video into packets instead of sending it as one large block of data.[3]
(b) Explain how the website's server puts the packets back together correctly.[2]
Show the answer and mark scheme
(a)
  • if a packet is lost or corrupted, only that packet has to be re-sent, not the whole 50 MB video
  • each packet can be checked for errors (e.g. using a checksum) when it arrives / an error only affects a small amount of data
  • each packet is given a header containing the destination IP address and a sequence number, so it can be delivered and put back in order
  • the receiving computer can acknowledge packets as they arrive, so the sender knows which packets need to be sent again
(b)
  • each packet has a sequence number in its header (added by TCP)
  • TCP on the server uses the sequence numbers to reassemble the packets in the correct order / asks for any missing packets to be re-sent

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