1.3.25

Layers

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Layering Concepts

Protocol layer models are often used to help conceptualise the many different network protocols.

Protocol layer models

Protocol layer models

In a protocol layer model, a protocol layer is simply a group or collection of network protocols that work at a similar level within the networking process.

Layer properties

Layer properties

Layers of a protocol layer model should be independent of each other.
Layers should only interact with each other by considering the inputs and outputs of that layer, not how it works.

Layers everywhere

Layers everywhere

Layers are not only used within networking.
Layers are one example of a technique called abstraction, which helps to simplify problems.
Layers are commonly used in software development. For example:
- A user interface layer.
- A processing layer.
- A database layer.

TCP and OSI Models

The four-layer Transmission Control Protocol model and the seven-layer Open Systems Interconnection model are two of the best known protocol layer models.

TCP model

TCP model

Application layer:
- Creates and interprets data (e.g. HTTP, IMAP, FTP).
Transport layer:
- Splitting / joining of data (e.g. TCP).
Internet layer:
- Adding addresses to data (e.g. IP).
Network Access layer:
- Converting data into electrical signal (hardware) (e.g. Ethernet, WiFi).

OSI model

OSI model

The OSI model is a very similar protocol layer model.
The OSI model has seven layers:
- Application.
- Presentation.
- Session.
- Transport.
- Network.
- Data Link.
- Physical.

Comparing the two models

Comparing the two models

The two models describe the exact same network system:
- The first three layers of the OSI model are grouped into TCP's 'Application' layer.
- The 'Transport' layers are the same in both models.
- OSI's 'Network' layer is called 'Internet' in the TCP model.
- OSI's bottom two layers are combined into TCP's 'Network Access' layer.

1

Computer Systems

1.1

Systems Architecture

1.1.1Fetch-Execute Cycle 1.1.2Common CPU Components & Their Function 1.1.3Von Neumann Architecture 1.1.4Factors Affecting CPU Performance 1.1.5Embedded Systems 1.1.6Exam-Style Questions - Von Neumann Architecture 1.1.7Diagnostic Misconceptions - Embedded vs General

1.2

Memory & Storage

1.2.1Types of Memory 1.2.2Flash Memory 1.2.3Properties of Flash Memory 1.2.4Running Out of Memory 1.2.5Virtual Memory 1.2.6Units of Capacity 1.2.7Calculating Capacity Requirements 1.2.8Solid State Storage 1.2.9Properties of Solid State Media 1.2.10Magnetic Storage 1.2.11Properties of Magnetic Media 1.2.12Examples of Magnetic Storage 1.2.13Optical Storage 1.2.14Properties of Optical Media 1.2.15Examples of Optical Storage 1.2.16Types of Optical Disk 1.2.17Number Bases 1.2.18Converting Number Bases 1.2.19Hexadecimal 1.2.20Using Hexadecimal 1.2.21Converting Denary & Hexadecimal 1.2.22Binary Addition 1.2.23Binary Shifts 1.2.24Representing Text 1.2.25ASCII & Unicode 1.2.26Representing Images 1.2.27Converting Binary & Images 1.2.28Representing Sound 1.2.29Data Compression 1.2.30Grade 9 - Storage 1.2.31Exam-Style Questions - Primary Memory 1.2.32Exam-Style Questions - Storage 1.2.33Exam-Style Questions - Data Conversions 1.2.34Diagnostic Misconceptions - RAM vs ROM 1.2.35Diagnostic Misconceptions - Bits, Nibbles & Bytes 1.2.36Diagnostic Misconceptions - Bits Required to Store 1.2.37End of Topic Test - Computer Systems 1.2.38End of Topic Test - Representation

1.3

Computer Networks, Connections & Protocols

1.4

Network Security

1.4.1Forms of Attack 1.4.2Penetration Testing 1.4.3Malware 1.4.4How Malware Spreads 1.4.5Social Engineering 1.4.6Phishing 1.4.7Cracking Passwords 1.4.8Denial of Service Attacks 1.4.9Data Interception 1.4.10Methods of Data Interception 1.4.11SQL Injection 1.4.12Network Administration 1.4.13Network Forensics 1.4.14Protecting Against Malware 1.4.15Firewalls 1.4.16User Access Levels 1.4.17Passwords 1.4.18Encryption 1.4.19End of Topic Test - Networks

1.5

Systems Software

1.5.1System Software 1.5.2Utility Software 1.5.3Operating Systems 1.5.4User Interfaces 1.5.5Memory & Process Management 1.5.6File Management 1.5.7Device Management 1.5.8User Management 1.5.9Encryption Software 1.5.10Defragmentation Software 1.5.11Data Compression Software 1.5.12Backup Software

1.6

Ethical, Legal, Cultural & Environmental Concern

2

Computational Thinking, Algorithms & Programming

2.1

Algorithms

2.1.1Computational Thinking - Abstraction 2.1.2Computational Thinking - Decomposition 2.1.3Algorithmic Thinking 2.1.4Pseudocode 2.1.5Flowchart Diagrams 2.1.6Interpreting Algorithms 2.1.7Correcting Algorithms 2.1.8Completing Algorithms 2.1.9Search Algorithms 2.1.10Binary Search 2.1.11Linear Search 2.1.12Overview of Sort Algorithms 2.1.13Bubble Sort 2.1.14Merge Sort 2.1.15Insertion Sort 2.1.16Exam-Style Questions - Sorting Algorithms

2.2

Programming Fundamentals

2.3

Producing Robust Programs

2.3.1Defensive Design 2.3.2Validation & Sanitisation 2.3.3Authentication & Contingencies 2.3.4Maintainability 2.3.5Purpose of Testing 2.3.6Types of Testing 2.3.7Test Plans 2.3.8Types of Errors 2.3.9End of Topic Test - Programming 2.3.10Exam-Style Questions - Testing

2.4

Boolean Logic

2.4.1Binary Systems 2.4.2Logic Circuits 2.4.3Boolean Logic 2.4.4Boolean Operators 2.4.5Grade 9 - Logic

2.5

Programming Languages & IDEs

2.5.1High-Level vs Low-Level Languages 2.5.2Translation - Compliers & Interpreter 2.5.3Translation - Assemblers 2.5.4Integrated Development Environments 2.5.5Exam-Style Questions - Translation

Jump to other topics

1

Computer Systems

1.1

Systems Architecture

1.1.1Fetch-Execute Cycle 1.1.2Common CPU Components & Their Function 1.1.3Von Neumann Architecture 1.1.4Factors Affecting CPU Performance 1.1.5Embedded Systems 1.1.6Exam-Style Questions - Von Neumann Architecture 1.1.7Diagnostic Misconceptions - Embedded vs General

1.2

Memory & Storage

1.2.1Types of Memory 1.2.2Flash Memory 1.2.3Properties of Flash Memory 1.2.4Running Out of Memory 1.2.5Virtual Memory 1.2.6Units of Capacity 1.2.7Calculating Capacity Requirements 1.2.8Solid State Storage 1.2.9Properties of Solid State Media 1.2.10Magnetic Storage 1.2.11Properties of Magnetic Media 1.2.12Examples of Magnetic Storage 1.2.13Optical Storage 1.2.14Properties of Optical Media 1.2.15Examples of Optical Storage 1.2.16Types of Optical Disk 1.2.17Number Bases 1.2.18Converting Number Bases 1.2.19Hexadecimal 1.2.20Using Hexadecimal 1.2.21Converting Denary & Hexadecimal 1.2.22Binary Addition 1.2.23Binary Shifts 1.2.24Representing Text 1.2.25ASCII & Unicode 1.2.26Representing Images 1.2.27Converting Binary & Images 1.2.28Representing Sound 1.2.29Data Compression 1.2.30Grade 9 - Storage 1.2.31Exam-Style Questions - Primary Memory 1.2.32Exam-Style Questions - Storage 1.2.33Exam-Style Questions - Data Conversions 1.2.34Diagnostic Misconceptions - RAM vs ROM 1.2.35Diagnostic Misconceptions - Bits, Nibbles & Bytes 1.2.36Diagnostic Misconceptions - Bits Required to Store 1.2.37End of Topic Test - Computer Systems 1.2.38End of Topic Test - Representation

1.3

Computer Networks, Connections & Protocols

1.4

Network Security

1.4.1Forms of Attack 1.4.2Penetration Testing 1.4.3Malware 1.4.4How Malware Spreads 1.4.5Social Engineering 1.4.6Phishing 1.4.7Cracking Passwords 1.4.8Denial of Service Attacks 1.4.9Data Interception 1.4.10Methods of Data Interception 1.4.11SQL Injection 1.4.12Network Administration 1.4.13Network Forensics 1.4.14Protecting Against Malware 1.4.15Firewalls 1.4.16User Access Levels 1.4.17Passwords 1.4.18Encryption 1.4.19End of Topic Test - Networks

1.5

Systems Software

1.5.1System Software 1.5.2Utility Software 1.5.3Operating Systems 1.5.4User Interfaces 1.5.5Memory & Process Management 1.5.6File Management 1.5.7Device Management 1.5.8User Management 1.5.9Encryption Software 1.5.10Defragmentation Software 1.5.11Data Compression Software 1.5.12Backup Software

1.6

Ethical, Legal, Cultural & Environmental Concern

2

Computational Thinking, Algorithms & Programming

2.1

Algorithms

2.1.1Computational Thinking - Abstraction 2.1.2Computational Thinking - Decomposition 2.1.3Algorithmic Thinking 2.1.4Pseudocode 2.1.5Flowchart Diagrams 2.1.6Interpreting Algorithms 2.1.7Correcting Algorithms 2.1.8Completing Algorithms 2.1.9Search Algorithms 2.1.10Binary Search 2.1.11Linear Search 2.1.12Overview of Sort Algorithms 2.1.13Bubble Sort 2.1.14Merge Sort 2.1.15Insertion Sort 2.1.16Exam-Style Questions - Sorting Algorithms

2.2

Programming Fundamentals

2.3

Producing Robust Programs

2.3.1Defensive Design 2.3.2Validation & Sanitisation 2.3.3Authentication & Contingencies 2.3.4Maintainability 2.3.5Purpose of Testing 2.3.6Types of Testing 2.3.7Test Plans 2.3.8Types of Errors 2.3.9End of Topic Test - Programming 2.3.10Exam-Style Questions - Testing

2.4

Boolean Logic

2.4.1Binary Systems 2.4.2Logic Circuits 2.4.3Boolean Logic 2.4.4Boolean Operators 2.4.5Grade 9 - Logic

2.5

Programming Languages & IDEs

2.5.1High-Level vs Low-Level Languages 2.5.2Translation - Compliers & Interpreter 2.5.3Translation - Assemblers 2.5.4Integrated Development Environments 2.5.5Exam-Style Questions - Translation

Practice questions on Layers

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

1
Which of these should a layer consider about other layers?Multiple choice
2
Are layers used only in networking?Multiple choice
3
Common layers in a software project might include:Fill in the list
4
Two common protocol layer models are:Fill in the list
5
Transmission Control Protocol ModelPut in order

Answer all questions on Layers

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Application Protocols

Advantages of Layering