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Networks (Protocols (Divided into layers (Advantages (Hardware is…

- - - - In charge of splitting data into packets and reassembling the packets back into the original data
      - Checks that data has been correctly sent and recieved
      - Transmission control protocol sets the rule for how devices connect on the network
    - - Simple mail transfer protocol- used to send emails and transfer them between servers
      - Internet message access protocol- used to retrieve emails from a server
      - Post office protocol- used to retrieve emails from a server
      - File transfer protocol- used to access, edit and move files between devices on a network
      - HTTP secure- encrypts all information sent and recieved
      - Hyper text transfer protocol- used by web browsers to access websites and communicate with web services
  - - - Converted into hexadecimal
      - Mainly used by the ethernet protocol on LANs
      - Read by LAN switches so they can direct data to the correct device
  - - - Hardware is universally compatible
      - Can be changed with no impact on other layers
      - Breaks networks down into manageable pieces
  - - - 1) The sending device splits the data into packets to be sent across the network. Each packet is given a packet number to show the order of the data.
        2) Each router reads the packet header and decides which way to send the packet next, according to the IP rules.
        3) The way the data is sent changes depending on network traffic so the packets can take different routes. If a router receives too many packets at once it may prioritise some over others.
        4) As the packets take different routes, they can arrive in the wrong order. The receiving device uses the packet numbers to reassemble them in the right order.
        5) Sometimes packets go missing in transit so the receiving device checks periodically that all packets have been received. If it hasn't received them in a certain time, it sends a timeout message back to the sending device.
        6) If all of the data is received and the checksums match, a receipt confirmation is sent to the sending device.
      - Used by routers
      - Directs the data
    - - Control information
        
        Destination address
        
        Source address
        
        Packet number
- - - - When a business uses it servers to store files of another organisation
      - Used of the internet to host websites
      - Used for general storage of user files and providing online software- this is CLOUD COMPUTING
      - It acts like an extension of a traditional client-server network
    - - Users can access files from any connected device
      - Easy to increase how much storage is available
      - No need to buy expensive hardware
      - No need to hire IT staff
      - Cloud host provides security and back-ups
      - Software is updated automatically
    - - Connection to the internet is required
      - Dependent on the host
      - Data can be vulnerable to hackers
      - Ownership unclear
      - Expensive usage and subscription fees
- - - - Suffers interference from adjacent channels
      - 2.4 GHz and 5 GHz
        
        2.4 has a better range and can pass through obstacles more easily
        
        5 GHz is faster over short distances
        
        Channels in the 2.4 GHz band overlap
        
        5 GHz band has more non-overlapping channels so there is less chance of interference
      - Standard for wireless networks
  - - - Transmit data as light
      - Don't suffer interference
      - Can transmit very large distances without loss of signal quality
      - High performance
    - - Single copper wire surrounded by a plastic layer for insulation
      - Metallic mesh provides shielding from outside interference
    - - CAT 5e and CAT6
        
        Twisted pair cables
        
        Four pairs of copper wires twisted to reduce internal interference
- - - - Rootkits- alter permissions
      - Spyware- secretly monitors user actions
      - Ransomware- locks files
      - Scareware- convince users the software is infected, and give a malicious link or request money
      - Deleting or modifying files
      - Open backdoors for later exploitation
    - - Viruses- attach to files and are spread by usres copying infected files. They are activated by users opening them.
      - Worms- self-replicate without any user help, and exploit weaknesses in network system.
      - Trojans- malware disguised as legitimate software tha are installed by users.
  - - - Way of gaining sensitive information or illegal access to networks by influencing people
      - A common form of social engineering takes place over the telephone- someone rings up an employee of a company and pretends to be a network administrator and asks them to disclose cofidential information
      - Phising is when a hacker directs a user to a spoof website of their company and asks them to update information
  - - - Specalists are employed to simulate potential attacks
      - Used to identify possible weaknesses
    - - Data is translated into a code which only someone with the correct key can access
      - Essential for sending data over a network securely
    - - Investigations undertaken to find the cause of attacks on a network
      - System of capturing data packets as thy enter a network
      - Packets can be analysised to discover how the network was attacked and decide how to prevent future attacks
    - - Regular testing to find and fix security weaknesses
      - Password protection
      - Enforce user access levels
      - Install anti-malware and firewall software to rpevent and destroy malicious software attacks
      - Encrypt sensitive data
    - - Prevent unauthorised users accessing the network
      - Should be strong, use a combination of letters numbers and symbols
    - - Designed to find and stop malware
      - Companies use firewalls to block unauthorised access by examining data traffic
    - - Controls which parts of a network users can access
      - Limit number of people with access to important data
      - Reduces insider attacks
- - - - Expensive wired setup, cheap when wireless
      - No single point where the network can collapse
      - Send data along the fastest route
      - Decentralised network
      - Full mesh- every device is connected to every other device
      - Partial mesh topology- every device is only connected to some of the other devices
    - - Data sent both ways, causing frequent data collisions
      - All devices are connected to a single backbone cable
      - Arranged in a line
    - - Data can pass through many devices before reaching the target device
      - Only one device can send data at a time
      - Data moves in one direction
    - - Disadvantages
        
        Wired setups can be expensive
        
        Server dependency
      - Advantages
        
        Few data collisions
        
        Simple to expand the network
        
        Device failure does not affect the rest of the network
      - Wired or wireless
      - All devices are connected to a central server
  - - - Faster and more reliable
      - Fibre optic cables are better than copper cables
    - - Depends on signal quality
- - - - Sharing files is easier
      - Users can work collaboratively
      - Hardware is shared
      - Internet connection is sharedSoftware can be updated simultaneously
      - Easy communication
      - User accounts can be stored centrally
- - - - Less reliable
      - Difficult to keep track of files
      - Complicated backups
      - No centralised management
  - - - Easy to keep track of files
      - Easy to perform backups
      - Easy to install and update software
      - Easier to manage network security
      - Servers are very reliable
    - - Expensive to set up
      - Needs IT specialists to maintain the network and server
      - Server dependence
      - Server can become overloaded