The Concept of Layers (AQA GCSE Computer Science)

Revision Note

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Robert Hampton

Written by: Robert Hampton

Reviewed by: James Woodhouse

The Concept of Layers

  • Networks rely on many complex parts all working together at the same time, from different types of network, the different operating models, the internet, wired and wireless to encryption, addressing and protocols

  • Managing the complexity of networks is helped with the use of layers

What is a layer?

  • A layer is a sub part of a more complex task

  • Dividing network tasks into layers reduces the complexity and makes each layer more manageable

  • An example of layers can be seen in the TCP/IP protocol which uses a 4-layer model known as a 'stack'

What are the advantages of layers?

  • Layers are self-contained which makes managing, repairing and upgrading easier as each layer can be worked on independent of other layers

  • Layers allow for focus on specific parts of a protocol without affecting other layers

  • Promotes data exchange (interoperability) between hardware and software

Examiner Tips and Tricks

In the exam you are required to understand the concept of layers AND describe the main function of TCP/IP layers

TCP/IP Model

What is the TCP/IP model?

  • The TCP/IP model is made up of two protocols (TCP & IP), containing 4 layers, that work together to package, address, transmit and receive data on a wide area network (Internet)

  • There are four layers that make up the TCP/IP protocol stack:

    • Application

    • Transport

    • Internet

    • Link

  • Different protocols operate on different layers

image1-1

Layer

Function

Protocols

Application

Application software such as web browsers and email clients operate here

HTTP, HTTPS, FTP, SMTP, IMAP

Transport

Enables communication between two hosts to agree settings such as size of packets

TCP, UDP

Internet

Addresses and packages data for transmission. Routes the packets across the network

IP

Link

Physical network hardware such as NIC is located, OS device drivers also sit here

 

Examiner Tips and Tricks

The link layer can sometimes be referred to as the ‘network access layer’ or ‘network interface layer’, you are not expected to remember the alternative names in this exam!

Worked Example

TCP/IP is a set of protocols based on layers.

  1. With regards to network protocols, define what is meant by a ‘layer’ [1]

  2. Describe one advantage of using layers to construct network protocols [2]

Answers

  • Breaking up a complex task into more manageable sub tasks

  • Self-contained

  • …it allows different developers to concentrate on one aspect of the network 

  • A layer can be taken out and edited without affecting other layers…

  • …it promotes interoperability between vendors and systems

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Robert Hampton

Author: Robert Hampton

Expertise: Computer Science Content Creator

Rob has over 16 years' experience teaching Computer Science and ICT at KS3 & GCSE levels. Rob has demonstrated strong leadership as Head of Department since 2012 and previously supported teacher development as a Specialist Leader of Education, empowering departments to excel in Computer Science. Beyond his tech expertise, Robert embraces the virtual world as an avid gamer, conquering digital battlefields when he's not coding.

James Woodhouse

Author: James Woodhouse

Expertise: Computer Science

James graduated from the University of Sunderland with a degree in ICT and Computing education. He has over 14 years of experience both teaching and leading in Computer Science, specialising in teaching GCSE and A-level. James has held various leadership roles, including Head of Computer Science and coordinator positions for Key Stage 3 and Key Stage 4. James has a keen interest in networking security and technologies aimed at preventing security breaches.