weak points

• A client -server model is where a clients creates requests for servers and the servers fulfil these requests.
• what is a client server model

  where the client makes requests to the server and the server responds.
• peer to peer models are networks that don't require a central server or switch. Each computer is directly connected to each other. Computers can act as a client or a server
• Advantages of Client-server :

  • Easier to track files because they're stored centrally
  • Easier to perform backups
  • Easier to install or update software
  • Easier to manage security🔐
• Disadvantages of Client server:

  • More expensive to maintain network and server 🤑
  • Dependant on server - if there's a problem with server, it affects entire network
  • May need IT specialists to maintain it
  • Server may be overloaded if there are too many clients 😵
• Advantages of Peer to Peer:

  • Cheaper 🤏
  • No dependence on server - if server fails, whole network isn't affected 💪
  • Easy to maintain - no expensive hardware
• Disadvantages of Peer to Peer:

  • No central server ∴ no centralised management
  • ... meaning backups and updates are complicated
  • Files have to be duplicated whilst being transferred👩👩
  • .....therefore hard to know which file is up to date
  • Peers may slow down and lose connection when being accessed🐢
  • Less reliable
• Types of errors in programs

  • Syntax
  • Logic
  • Run-Time Errors
• IDEs will often be written for specific high level languages (e.g. PyScripter is built for Python), but some support the writing of a number of different languages
• Cables (Ethernet)

  There are two main types of cable which can transport data between computers using ethernet:

  Copper Cables:

  These are made up of twisted pairs of copper wires with the data being transported via electrical signals. Because they carry electrical signals, they can suffer from interference.

  Fibre Optic Cables:

  These are made up of glass fibres with the data being transported via light signals. Fibre optic cables are more effective…nothing travels faster than the speed of light! They also do not suffer from interference. They are however more expensive than Ethernet cables.
• Wireless (Bluetooth)

  Bluetooth is another wireless data transfer medium, allowing devices to connect and share data without wires

  • Bluetooth can only support data transfer between a small number of devices at any one time
  • Bluetooth has a shorter range than Wi-Fi and as such, two communicating devices will need to be relatively close to one another for the transfer of data to work
  •  Bluetooth is generally easier to use/setup
  •  Generally less secure than Wi-Fi.
• Wireless (Wi-Fi)

  • Wi-Fi allows network access to portable devices by using radio waves to send data (not wires!).
  • Wi-Fi is a ‘standard’. This means that all Wi-Fi devices are using the same standard technology. In particular they send and receive data using standard radio frequency bands
• Data Packets

  • When files are sent over the internet they are split into millions of data packets.
• Open Source🤏💕

  • Software where the source code is freely available to the public
  • Users may legally modify the source code and it can be shared under the same licence and terms as the original software
• Advantages of Open Source :

  • It is FREE
  • Encourages collaboration
  • Big projects will be maintained by a community where they help to improve software and fix any errors or bugs
  • Therefore it also encourages rapid development
• Disadvantages of Open Source:

  • No Warranties. No customer support. No guarantee
  • Small projects may not get regular updates
  • ...and so it could have bugs 🦟
  • ...or it may not be secure 🔐
• The 5 Major Roles of the Operating System

  • Memory Management
  • Peripheral Management
  • Multi-Tasking
  • Security
  • User Interface
• Penetration Testing

  • Organisations employ specialists to stimulate attacks on their networks
  • This is effective because it helps organisation identify potential weaknesses on their network
• Passwords

  • Prevents unauthorised users accessing information
  • Using strong passwords or Two factor authentication is effective against Brute Force attacks
• HTTP(Hypertext Transfer Protocol) is the protocol used to transfer data between web browsers and web servers. Allows web browsers to access websites

  HTTPS(Hypertext Transfer Protocol Secure) is the secure version of HTTP. However, it ENCRYPTS all of the data sent and received
• FTP(File Transfer Protocol) is used to access edit and move files on a network
• TCP(Transmission Control Protocol) is a protocol that is used to send data across a network by splitting data into packets .

  • It makes sure that the data was sent to the right destination
  • Makes sure that the data is the same once it has reached its destination
• IP(Internet Protocol)

  • Controls and routes where data should be sent
  • Uses the IP address to send it to the right location
• SMTP(Simple Mail Transfer Protocol) is used to send emails from one server to another.
• IMAP(Internet Message Access Protocol) is a protocol that allows you to access email from a web browser.

  • The server will hold onto the email until you delete it
• POP(Post Office Protocol) is used to send email from one server to another

  • Once the email is downloaded, it is deleted
• What does the SMTP protocol do?


  Sends emails between server
• MAC Address is a unique identifer which is assigned to hardware devices that can be connected to a network. They are 48 or 64 bit.And they're assigned by manufacturer
• A layer is a group of protocols with similar functions . Each layer serves the layer above it.Data can only be passed between adjacent layers.
• Advantages of layers:

  • Breaks network communication into manageable pieces
  • Therefore it's easier for developers to concentrate on one area without having to worry about others
  • Having standards makes companies create hardware that is compatible
• SQL Injection

  • Used to access data in databases
  • SQL Injections are typed into a websites input box
  • This will then reveal sensitive info
• Firewall

  • Blocks unauthorised access 🚫
• Advantages of Proprietary Software

  • Has a warranties and guarantee
  • Has customer support
  • Source code cannot be stolen: license required to view
  • Should be tested and reliable
• Disadvantages of Proprietary Software

  • Can be expensive
  • It cannot be changed , therefore it may not fit users needs
  • Older versions may not be maintained well
  • May be less secure and contain bugs
• Fragmentation happens when deleted files create spaces which may not be big enough for new files. Therefore, the new files are split up.

  • Files that are fragmented take a longer time to read or access files because of the distance between the fragmented pieces
• Utility Software

  • This configures and maintains a computer system
  • increase user experience
• Factors that affect network performance:

  • Bandwidth
  • Latency
  • Range
  • Number of users or devices
  • Interference(Thick Walls)
• Bandwidth:

  • how much data can be transferred in a specific amount of time
  • Measured in Mbps(Megabits per second)
• Latency:

  • The delay in the time it takes data to transfer from one place to another
• Range:

  • The maximum distance for a device to have a good network connection
  • If the range is high, the weaker the connection