The Concept of Layers (AQA GCSE Computer Science)
Revision Note
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 Tip
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
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 Tip
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.
With regards to network protocols, define what is meant by a ‘layer’ [1]
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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