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J277 1.3.2 Protocols and layers

Part 6 of 7 · J277 1.3 · Networks

The protocols named in OCR J277 and the reason they are organised into layers.

Students will:

  • explain the principle of a communication protocol
  • match TCP/IP, HTTP, HTTPS, FTP, SMTP, POP and IMAP to their purposes
  • describe the differences between closely related protocols
  • select protocols for a scenario
  • explain how protocols are layered and why that helps

Inside: 5 text sections, 1 multiple-choice activity, 5 completion activities, 5 written answers. 23 marks. Suggested teaching time: 45–65 minutes. 1 diagram.

Includes a teacher guide with suggested sections, timings and common misconceptions.

Series: J277 1.3 · Networks, part 6 of 7.

Shared by Coding PathwayVerified teacher

  • 16 cells
  • About 60 minutes
  • CC BY-SA 4.0
  • Shared 17 Aug 2026
  • Updated 27 Oct 2026

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The whole resource, exactly as a class sees it. Answers and marking are held back.

Protocols and layers

A communication protocol is an agreed set of rules for transferring data. Rules can cover the message format, addressing and checking. Both systems need compatible rules. Different jobs need different protocols.

Written answer1 mark

State what is meant by a communication protocol.

Students type their answer here.

1. Web and file transfers

ProtocolPurpose
HTTP (Hypertext Transfer Protocol)Transfers web pages and related data between a browser and web server. Ordinary HTTP does not encrypt the transfer.
HTTPS (HTTP Secure)Transfers web data using encryption, protecting information such as a password while it travels.
FTP (File Transfer Protocol)Uploads and downloads files between computers, often a client and server. Ordinary FTP does not provide encryption.

HTTPS protects data in transit. It does not prove that everything on a website is trustworthy.

Fill in the blanks3 marks
Answer 1 transfers web content without added encryption. Answer 2 provides encrypted web transfers. Answer 3 transfers files using File Transfer Protocol.
  • FTP
  • HTTP
  • HTTPS
  • SMTP
  • IP

2. TCP and IP work together

TCP/IP means Transmission Control Protocol / Internet Protocol.

  • TCP divides data into packets and supports reliable delivery. It checks receipt, requests missing data again, puts packets in order and reassembles the data.
  • IP supplies addressing and routing. Routers use a packet's destination IP address to forward it towards the right network.

Packets do not have to arrive in the order in which they were sent.

Multiple choice1 mark

Packets need to be forwarded between networks towards a destination. Which statement describes the relevant role?

  • ASMTP finds a web server's IP address
  • BIP supplies addressing and routing
  • CTCP stores the user's email inbox
  • DHTTP assigns a MAC address to every router
Written answer2 marks

A file is sent as packets. Some packets arrive out of order and one packet does not arrive. Describe two actions TCP can take to reconstruct the file correctly.

Students type their answer here.

3. Email: send or receive?

ProtocolPurpose
SMTP (Simple Mail Transfer Protocol)Sends email from a client to a mail server and between mail servers.
POP (Post Office Protocol, often POP3)Downloads received email from a mail server for local storage. Settings can leave or remove the server copy.
IMAP (Internet Message Access Protocol)Accesses email kept on a mail server and synchronises mailbox changes across devices.

Deleting or reading an email through IMAP can be reflected on your other devices. POP's local downloads do not provide that same shared mailbox view.

Fill in the blanks3 marks
Answer 1 sends email. Answer 2 downloads received email for local storage. Answer 3 accesses a server-held mailbox and synchronises changes across devices.
  • POP
  • FTP
  • IMAP
  • SMTP
  • HTTP
Fill in the blanks3 marks
Choose a suitable protocol taught in this worksheet for each task. (a) A charity website receives a volunteer's password using encrypted web communication: Answer 1 (b) A designer uploads image files from a computer to a remote server: Answer 2 (c) A mail client sends an email to its mail server: Answer 3
Written answer2 marks

A volunteer needs the same email mailbox on a phone and a laptop. Explain why IMAP is suitable.

Students type their answer here.

Written answer1 mark

State one purpose of POP in email communication.

Students type their answer here.

4. Share the work between layers

A protocol system divides communication into layers. Each layer handles part of the job and uses services provided by the layer below it. Data moves down the sending system's layers, across the connection and up the receiver's layers.

This makes a complex task easier to design, test and troubleshoot. One layer can be improved without redesigning all the others. Its interfaces, the rules for communicating with neighbouring layers, must stay compatible. The diagram shows four layers; their names are not needed here.

Data passes through layers on both devices Four unnamed layers are shown on each of a sending and receiving device. Data moves down the sender, crosses the network connection at the bottom and moves up the receiver. Each layer handles part of communication; the diagram does not ask for layer-name recall. Sender Receiver Top layerLayerLayerBottom layer Top layerLayerLayerBottom layer Link Down, across, then up. Each layer handles part of the job.
Fill in the blanks3 marks
Communication is split into Answer 1. Keeping the Answer 2 compatible allows one layer to change more Answer 3.
  • independently
  • layers
  • addresses
  • interfaces
  • bandwidth
Written answer2 marks

A developer improves one layer in a network protocol system. Explain how using layers can reduce the work needed on the rest of the system.

Students type their answer here.

Fill in the blanks2 marks
Name the protocol for each job without using the tables. (a) Sending email to a mail server: Answer 1 (b) Accessing web pages using the unencrypted Hypertext Transfer Protocol: Answer 2