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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: 6 explanation cells, 2 multiple-choice questions, 3 fill-in-the-blanks cells and 4 written answers. 42 marks, about 75 minutes.

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

Shared by Coding PathwayVerified teacher

  • 15 cells
  • About 75 minutes
  • CC BY-SA 4.0
  • Shared 17 Aug 2026
  • Updated 9 Sept 2026

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

Networks 6: protocols and layers

Addresses tell data where to go. Protocols provide the agreed rules for transferring it.

By the end, you should be able to:

  • explain the principle of a communication protocol
  • match TCP/IP, HTTP, HTTPS, FTP, SMTP, POP and IMAP to their purposes
  • describe key differences between related protocols
  • select protocols for a scenario
  • explain how protocols are organised into layers
  • explain the benefits of using layers

OCR does not require port numbers or the names and functions of every TCP/IP layer. Work through the explanation, checks and applications in order. Use the final challenge to connect several network ideas.

1. Protocols are agreed communication rules

A communication protocol is a set of agreed rules for transferring data. The rules can cover how data is formatted, addressed, sent, received and checked.

Both communicating systems must follow compatible rules. Different protocols are used for different purposes, just as different services have different requirements.

A protocol is not a piece of hardware and it does not describe one physical cable. It is the rule set followed by hardware and software during communication.

Fill in the blanks5 marks
A communication label 1 is a set of agreed label 2 for label 3. The rules can define the label 4 of a message, and different protocols are chosen for a different label 5.
  • protocol
  • hardware
  • rules
  • transferring data
  • purpose
  • format

2. Protocols for networks, the Web and files

TCP/IP

TCP/IP means Transmission Control Protocol and Internet Protocol. These protocols work together to support communication across networks, including the Internet.

  • TCP divides data into packets, checks that packets arrive, places them in the correct order and reassembles the original data at the destination. It supports reliable, ordered delivery.
  • IP provides addressing and routing. Routers use the destination IP address to forward packets across networks towards the correct device.

HTTP, HTTPS and FTP

HTTP, Hypertext Transfer Protocol, transfers web pages and related data between web clients and web servers. Standard HTTP traffic is not encrypted.

HTTPS, Hypertext Transfer Protocol Secure, performs the same web transfer role with encryption added. It protects sensitive data such as login or payment information while it is transferred.

FTP, File Transfer Protocol, transfers files between computers, commonly between a client and a server. It can upload or download files.

3. Protocols for email

Different protocols perform the sending and receiving roles.

  • SMTP, Simple Mail Transfer Protocol, sends email from a client to a mail server and between mail servers.
  • IMAP, Internet Message Access Protocol, keeps the mailbox managed on the mail server and synchronises messages and changes across devices.
  • POP, Post Office Protocol and commonly POP3, downloads messages from a mail server for local storage on a device. Depending on its settings, the server copy may be removed after download, so POP is less suitable when one mailbox must stay synchronised across several devices.

A concise memory aid is: SMTP sends; IMAP or POP receives.

Fill in the blanks7 marks
label 1 supports communication across interconnected networks. label 2 transfers ordinary web content, while label 3 adds security for web data. label 4 transfers files. label 5 sends email, while label 6 and label 7 retrieve or access received email.
  • FTP
  • SMTP
  • TCP/IP
  • HTTPS
  • HTTP
  • Bluetooth
  • Ethernet
  • IMAP
  • POP
Multiple choice, several answers3 marks

Which statements correctly distinguish TCP from IP? Select all that apply.

  • AIP synchronises an email inbox across devices
  • BTCP divides data into packets and reassembles it at the destination
  • CTCP converts a domain name into an IP address
  • DTCP checks packet delivery and order
  • EIP provides addressing and routing across networks
Written answer4 marks

A user reads the same mailbox on a phone, laptop and tablet. Recommend IMAP or POP and justify the choice.

Use: 'I recommend... because messages... This means the phone, laptop and tablet...'. Contrast this with how POP downloads messages.

Students type their answer here.

Written answer5 marks

A business needs to open a public information page, sign in securely, upload a large file to its server, send an email and then read the reply on several devices. Select a suitable protocol for each task.

Create five short pairs: 'Task: protocol because purpose'. More than one receiving protocol exists, so match the choice to the several-device requirement.

Students type their answer here.

4. The concept of layers

Network communication is complex, so protocol systems divide the work into layers. Each layer handles a particular part of communication and provides a service to the layer above it. Data passes through layers on the sending system and through corresponding layers on the receiving system.

The four-layer TCP/IP model is a useful teaching example, but you do not need to memorise the name and function of each layer for OCR J277.

Benefits of layers include:

  • simpler design: a complex communication task is divided into manageable parts
  • easier development and testing: each layer can be considered separately
  • easier fault finding: a problem can be located within part of the system
  • independent change: one layer can be updated without redesigning every other layer, provided the interfaces remain consistent
  • consistent interfaces: developers can improve one part while keeping its communication with neighbouring layers predictable
Matching protocol layers on two communicating devices Data moves down a stack of unnamed layers on the sending device, across the connection and up matching layers on the receiving device. Each layer handles part of communication and can change independently if its interface remains compatible. Sending deviceReceiving device top layerlayerlayerbottom layertop layerlayerlayerbottom layer data moves down data moves up network connection
Fill in the blanks5 marks
A protocol system divides communication into label 1, turning one complex task into label 2. A layer can often be changed more label 3 when its label 4 stays consistent, and separation can make label 5 easier.
  • manageable parts
  • bandwidth
  • layers
  • independently
  • interface
  • fault finding
Multiple choice, several answers3 marks

Which are benefits of organising protocols into layers? Select all that apply.

  • AComplex communication is divided into manageable parts
  • BEvery network is guaranteed unlimited bandwidth
  • CA layer can be developed or changed with less effect on other layers
  • DAll addresses and security controls become unnecessary
  • EFault finding can focus on one part of the process
Written answer4 marks

Explain two benefits of using layers in network protocols.

For each point use: 'Layers allow... This helps because...'. Apply the effect to simpler design, separate testing, fault finding or changing one layer with less effect on others.

Students type their answer here.

Written answer6 marks

Challenge: a student securely uploads coursework to a school web service and receives a confirmation email on several devices. Explain how protocols and layers support this communication.

Use two sections. First select and justify the protocols for upload and email. Then explain one benefit of organising those rules into layers. Do not name individual TCP/IP layers.

Students type their answer here.

Final check

Without looking back, write the seven protocol names and match each to one purpose. Then explain two benefits of layers using a complete cause-and-effect sentence for each.

Check that you can:

  • define a protocol as agreed rules for transferring data
  • match TCP/IP, HTTP, HTTPS, FTP, SMTP, POP and IMAP to suitable tasks
  • distinguish HTTP from HTTPS and POP from IMAP
  • select protocols from a scenario
  • explain the concept and benefits of layers without relying on memorised layer names