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Computer networks, connections and protocols - Coggle Diagram

- - - - Time taken for a data packet to travel through a network
      - Lower latency means less delay
      - Important for online gaming and video calls
    - - Amount of data that can travel through a connection at a time
      - Higher bandwidth allows more data to be transmitted
      - Measured in Mbps (megabits per second)
    - - Error rate: How often data is corrupted or lost; higher rate means more retransmissions and slower performance
      - Collisions: When devices transmit simultaneously, causing data interference and requiring retransmission
  - - - Expensive hardware
      - Large networks are complicated to manage
      - Viruses can spread across the network
    - - Share resources, e.g. printers
      - Access files from any connected computer
      - Centralised storage makes backups easier
    - - Connects networks across large geographical distances
      - Uses third-party carriers, e.g. BT.
      - Uses cables, telephone lines, satellites or radio waves
      - Example: universities, banks and governments connecting multiple sites
    - - Connects computers within a small geographical area, e.g. school, home or business
      - Uses the organisation's own cabling and equipment
  - - - Central server provides services/resources to clients
      - Client requests resources and receives a response
      - Server processes requests and sends back the requested data
    - - File server - stores files and manages backups
      - Print server - manages printing across the network
      - Email server - receives, filters and distributes emails
      - Web server - hosts websites
      - Database server - stores information, e.g. student records
    - - Centralised backups and security
      - Resources easily shared
      - Can support hundreds or thousands of users
    - - Users depend on the central server
      - Server failure can disrupt services
    - - No central server
      - Computers communicate ans share files directly
      - Each computer can provide resources to others
    - - Easy to set up
      - No dedicated server equipment required
      - Computers can share files and hardware
    - - Each computer needs its own backup
      - Security is managed individually
      - Files are not centrally organised
      - If a computer is switched off, its files are unavailable
      - Difficult to maintain with many computers
  - - - Allows a device to connect to a network
      - Can be wired or wireless
      - Usually built into modern devices
    - - Connects devices within a LAN
      - Uses MAC addresses to send data to the correct device
      - A hub sends data to every connected device instead
    - - Directs data packets towards their destination
      - Connects a LAN to other networks, including the Internet
    - - Reqiuired to connect to the Internet
      - Often combined with a router
    - - Allows wireless devices to connect to a wire dnetwork
      - Usually connects to a router
  - - - Data is split into smaller packets before transmission
      - Each packet contains:
        
        Source IP address
        
        Destination IP address
        
        Sequence number
        
        Total number of packets
        
        Error checking data
      - Packets can take different routes
      - Receiver reassembles packets in the correct order
      - Corrupt or missing packets can be requested again
    - - Translates domain names into IP addresses
      - E.g. converts google.com into its IP address
      - DNS servers pass requests to other servers if they cannot find the address
    - - Advantages
        
        Access files from anywhere with internet access
        
        Easy to share files and collaborate
        
        Reduces the need for local storage
        
        Cloud providers manage maintenance and backups
      - Cloud computing
        
        Definition: Using remote servers accessed over the Internet to store, manage and proccess data, rather than relying entirely on your own device
        
        Data and software are stored on servers in data centres
        
        Users can access files and applications from different devices, provided they have an internet connection
      - Disadvantages
        
        Requires an internet connection
        
        Security and privacy risks when storing data online
        
        Services can become unavailable if the provider has problems
        
        Ongoing subscription costs may apply
      - Examples: Google Drive, OneDrive and iCloud
    - - Identifies devices on a network
      - IPv4: four 8-bit numbers, each between 0-255, separated by dots
      - IPv6: 128-bit address represented in hexadecimal
    - - One service that uses the Internet
      - Collection of interlinked web pages and resources
      - Accessed using a web browser
      - Uses HTTP to send and receive data
    - - Routers direct packets between networks
      - Internet routers send packets towards their destinations
    - - A worldwide collection of interconnected networks
      - The largest WAN in the world
      - Supports services including email, file sharing and VoIP
  - - - The way devices and connections are arranged within a network
    - - Every device connects to a central switch
      - Advantages
        
        Fast data transfer
        
        If one cable fails, other devices remain connected
      - Disadvantages
        
        Requires additional hardware and cables
        
        If the central switch fails, the entire network goes down
    - - Devices connect to multiple other devices
      - Nodes can act as routers, passing data through the network
      - Full mesh: every node connects to every other node
      - Partial mesh: only some nodes have multiple connections
      - Advantages
        
        Resilient - no single point of failure
        
        Data can travel along alternative routes
        
        Can be ecpanded witout disrupting the network
      - Disadvantages
        
        Epensive to install
        
        Can have redundant connections
        
        Difficult to maintain
    - - Uses a combination of networks, with many parts operating as a partial mesh
      - Alternative routes allow packets to be redirected if a connection fails
- - - - Protects data from being understood if intercepted
      - Converts readable data into an encoded form
    - - Plaintext – original readable message
      - Ciphertext – encrypted message
      - Encryption – converting plaintext into ciphertext
      - Decryption – converting ciphertext back into plaintext.
      - Key – information used to encrypt or decrypt data
      - Encryption algorithm – method/formula used to encrypt data
    - - Same key encrypts and decrypts the data
      - Key must be shared with the recipient
      - Risk: someone intercepting the key could decrypt the message
    - - Uses two keys:
        
        Public key – encrypts data; can be shared
        
        Private key – decrypts data; kept secret
      - More secure because the private decryption key does not need to be shared
    - - WEP – older, insecure encryption standard; can be cracked easily
      - WPA – improved wireless security
      - WPA2 – newer and more secure than WEP
      - HTTPS – encrypts data sent between a browser and website
  - - - Wi-Fi
        
        Uses radio waves to connect devices to a network
        
        Used by computers, smartphones and IoT devices
        
        Requires a wireless NIC and access point
      - Bluetooth
        
        Connects devices over short distances
        
        Uses 2.4 GHz radio waves
        
        Typically works within 10 metres
        
        Devices must be paired before connecting
      - Wireless transmission disadvantages
        
        Signals can be blocked by walls and objects
        
        Interference from other devices
        
        Generally slower than wired connections
        
        Greater security risks
    - - Fibre optic cables
        
        Transmit data using light
        
        Very fast transmission
        
        Low signal loss over distance
        
        Not affected by electromagnetic interference
        
        Disadvantages: expensive equipment and installation
      - Copper cables
        
        Transmit data using electrical signals
        
        Relatively inexpensive and reliable
        
        Disadvantages: affected by electromagnetic interference, lower bandwidth and heavy cables
      - Ethernet
        
        Common wired networking technology
        
        Usually uses twisted-pair copper cables
        
        Can also use fibre optic cables
  - - - Identifies a device's location on a network
      - Used to route packets to their destination
      - IPv4 uses four 8-bit numbers (0–255)
      - IPv6 uses 128 bits and hexadecimal
      - Can change when a device connects to a different network
      - Dynamic IP address – an address that can change
    - - Unique identifier assigned to a NIC by its manufacturer
      - Usually does not change
      - Written in hexadecimal
      - Used to identify devices on a local network
      - Switches use MAC addresses to send data to the correct device
    - - IP identifies network location; MAC identifies network interface
      - IP can change; MAC normally permanent
      - IP used for routing between networks; MAC used for communication on local networks
  - - - 802.11b/g/n – uses 2.4 GHz
      - 802.11a/n/ac – uses 5 GHz
    - - Greater range
      - Better at covering larger areas
      - More interference because the frequency is crowded
    - - A family of rules governing wired local networking
      - Defines how data is formatted for transmission
      - Devices wait until a connection is quiet before transmitting
      - If two devices transmit simultaneously, they stop and wait a random time before trying again
    - - Higher data transmission rates
      - Less interference
      - Less able to penetrate walls
  - - - Requests and receives web pages from web servers
    - - Secure version of HTTP
      - Encrypts information sent between browser and website
    - - Transfers files to and from an FTP server
    - - Sends emails from a device to a mail server
      - Relays emails between mail servers
    - - Downloads emails from a mail server to a local device
      - Messages may then be removed from the server
    - - Accesses emails stored on a mail server
      - Allows emails to be accessed from multiple devices
    - - Splits messages into packets
      - Reassembles packets at the destination
      - Detects errors and resends lost packets
    - - Routes individual packets between IP addresses
  - - - Divides network communication into four layers
      - Each layer has a specific responsibility
      - Allows different hardware and software to communicate
    - - Application layer
        
        Applications create data
        
        Protocols: HTTP, HTTPS, FTP, SMTP, POP, IMAP
      - Transport layer
        
        Splits data into packets
        
        Numbers packets and reassembles them
        
        Resends lost packets
        
        Protocol: TCP
      - Internet layer
        
        Routes packets between networks
        
        Adds source and destination IP addresses
        
        Protocol: IP
      - Link layer
        
        Handles communication over the physical network
        
        Uses MAC addresses
        
        Technologies: Ethernet and Wi-Fi
    - - Internet layer adds IP addresses and routes packets
      - Transport layer splits it into packets
      - Application creates the data
      - Link layer handles transmission through network hardware
    - - Link layer processes the incoming data
      - Internet layer removes IP addressing information
      - Transport layer reassembles packets
      - Application layer displays the data to the user
    - - Each layer is self-contained
      - One layer can be changed without affecting the others
      - Different manufacturers' hardware and software can work together
      - Makes communication between different systems possible