What are network protocols, and why are networks organised into layers?
Common network protocols (TCP/IP, HTTP, HTTPS, FTP, POP, IMAP, SMTP), the concept of layers and the benefits of using them.
An OCR J277 1.3.2 answer on the common network protocols (TCP/IP, HTTP, HTTPS, FTP, POP, IMAP, SMTP), what a protocol is, the concept of network layers and the benefits of using a layered model.
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What this dot point is asking
OCR wants you to state what a protocol is and the purpose of the named protocols, to explain what a layer is, and to give the benefits of a layered model. The email protocols (SMTP, POP, IMAP) and the web protocols (HTTP, HTTPS) are commonly confused, so learn exactly which does what.
What a protocol is
The common protocols
Layers
Why this matters
The protocols and layers together let the internet work despite being built from countless different devices and made by different companies. Agreed protocols mean any browser can talk to any web server; layering means the people who design a Wi-Fi chip do not need to know how a web page is built, only how to pass data to the layer above. For the exam, be able to name each protocol's job and give a couple of clear benefits of layering.
Try this
Q1. State the purpose of the HTTPS protocol. [1 mark]
- Cue. To request and receive web pages securely, encrypting the data between browser and server.
Q2. State which protocol is used to send email and which two are used to retrieve it. [2 marks]
- Cue. SMTP sends; POP and IMAP retrieve.
Q3. Give one benefit of organising a network into layers. [1 mark]
- Cue. Any of: breaks the system into manageable parts; each layer can be changed independently; different manufacturers' equipment can work together; easier troubleshooting.
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 20204 marksState the purpose of each of the following protocols: HTTPS, FTP, SMTP and IMAP.Show worked answer →
Award one mark for each correct purpose, up to four.
HTTPS (Hypertext Transfer Protocol Secure): used to request and receive web pages securely, encrypting the data between the browser and the web server (the secure version of HTTP).
FTP (File Transfer Protocol): used to transfer files between computers over a network, for example uploading files to a server.
SMTP (Simple Mail Transfer Protocol): used to send email from a client to a mail server and between mail servers.
IMAP (Internet Message Access Protocol): used to retrieve and manage email on a mail server, keeping the messages on the server so they can be accessed from multiple devices.
Markers reward the correct, specific purpose of each. Mixing up SMTP (sending) with IMAP/POP (retrieving) loses the mark.
OCR 20224 marksExplain what is meant by a layer in a network model, and give two benefits of organising a network into layers.Show worked answer →
A layer is a division of the network's functions into separate, self-contained levels, each responsible for a particular task (for example one layer handles the application, another the breaking of data into packets, another the addressing and routing, another the physical transmission). Each layer provides services to the layer above and uses the layer below.
Benefits (one mark each, up to two): it breaks a complex system into smaller, more manageable parts that are easier to design, understand and develop; each layer can be changed or updated independently without affecting the others, as long as the interfaces between them stay the same; it allows hardware and software from different manufacturers to work together if they follow the standards; and it makes troubleshooting easier because a problem can be isolated to one layer.
Markers reward a correct idea of a layer (a self-contained level handling one task) and two distinct benefits.
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Sources & how we know this
- OCR GCSE (9-1) Computer Science (J277) specification — OCR (2020)