Networks: How Do Packets Get Routed?

Packet Switching

Packet switching is the process of breaking data down into packets, sending them across the Internet to another computer, and then re-assembling the data.

Sender's local area network

The sender will generate data in an application on their computer.
- This happens at the application layer.
The data is split into packets of data.
- This happens at the transport layer.
Internet Protocol adds IP addresses to each packet.
- This happens at the Internet layer.
Packets are grouped into frames and sent to the router on the LAN.
- This happens at the Network layer.

Over the Internet

The sender's router inspects the packet to determine if the destination IP is on the current LAN.
- If it is not then it will send the packet onto the Internet (or other wide area network).
- This happens at the Internet layer.
Each packet is sent from the sender's router to the destination router via connected routers.
- The path of each packet can be different, which maximises efficient use of the network by avoiding bottlenecks.

Recipient's local area network

Because they have taken different paths, the packets at the destination will be in the wrong order.
- These packets are unpackaged and reassembled into the correct order using the sequence number of each packet.

1Computer Systems

1.1Systems Architecture

1.1.1Elements of Computer Systems

1.1.2Types of Computer Systems

1.1.3Von Neumann Architecture

1.1.4Registers of the Central Processing Unit (CPU)

1.1.5Fetch-Execute Cycle

1.1.6Factors Affecting CPU Performance

1.1.7Exam-Style Questions - Von Neumann Architecture

1.2Memory & 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

1.2.6Exam-Style Questions - Primary Memory

1.2.7Capacity

1.2.8Calculating Capacity Requirements

1.2.9Solid State Storage

1.2.10Properties of Solid State Media

1.2.11Magnetic Storage

1.2.12Properties of Magnetic Media

1.2.13Examples of Magnetic Storage

1.2.14Optical Storage

1.2.15Properties of Optical Media

1.2.16Examples of Optical Storage

1.2.17Types of Optical Disk

1.2.18End of Topic Test - Computer Systems

1.2.19Grade 9 - Storage

1.2.20Exam-Style Questions - Storage

1.2.21Number Bases

1.2.22Converting Number Bases

1.2.23Hexadecimal

1.2.24Using Hexadecimal

1.2.25Binary Addition

1.2.26Binary Shifts

1.2.27Representing Text

1.2.28ASCII & Unicode

1.2.29Representing Images

1.2.30Converting Binary and Images

1.2.31Representing Sound

1.2.32Data Compression

1.2.33End of Topic Test - Representation

1.2.34Exam-Style Questions -Data Conversions

1.3Computer Networks, Connections & Protocols

1.4Network 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

1.5Systems Software

1.5.1System Software

1.5.2Utility Software

1.5.3Operating Systems

1.5.4User Interfaces

1.5.5Memory and 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

1.6Ethical, Legal, Cultural & Environmental Concern

2Computational Thinking, Algorithms and Programming

2.1Algorithms

2.1.1Computational Thinking - Abstraction

2.1.2Computational Thinking - Decomposition

2.1.3Algorithmic Thinking

2.1.4Pseudocode

2.1.5Flow Diagrams

2.1.6Interpreting Algorithms

2.1.7Correcting Algorithms

2.1.8Completing Algorithms

2.1.9Search Algorithms

2.1.10Linear Search

2.1.11Binary Search

2.1.12Overview of Sort Algorithms

2.1.13Bubble Sort

2.1.14Insertion Sort

2.1.15Merge Sort

2.1.16Exam-Style Questions - Sorting Algorithms

2.2Programming Fundamentals

2.2.1Variable Declaration and Assignment

2.2.2Input and Output

2.2.3Program Flow - Sequence

2.2.4Program Flow - Selection

2.2.5Program Flow - Iteration

2.2.6Arithmetic Operators

2.2.7Relational Operators

2.2.8Boolean Operators

2.2.9Data Types

2.2.10Casting

2.2.11Arrays

2.2.12Strings

2.2.13File Handling

2.2.14Structuring Data - Records

2.2.15Structured Query Language

2.2.16End of Topic Test - Programming

2.2.17Exam-Style Questions - Translation

2.3Producing Robust Programs

2.3.1Defensive Design

2.3.2Validation and Sanitisation

2.3.3Authentication and Contingencies

2.3.4Maintainability

2.3.5Comments

2.3.6Purpose of Testing

2.3.7Types of Testing

2.3.8Test Plans

2.3.9Error Types

2.3.10End of Topic Test - Programming

2.3.11Exam-Style Questions - Testing

2.4Boolean Logic

2.4.1Binary Systems

2.4.2Logic Circuits

2.4.3Boolean Logic

2.4.4Boolean Operators

2.4.5Grade 9 - Logic

2.5Programming 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

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