GCSE Computing - Network Topologies

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  • Network Topologies
    • Star Network
      • This is the most common layout for a network.
      • All nodes are connected to a central device.
      • They are very fast and reliable.
      • There is a low chance of packet collision.
    • Mesh Network
      • All nodes are involved in the transmission of a message.
      • There is no central router needed.
      • They are very fault tolerant.
      • All nodes are connected to each other.
      • If a route is blocked, the routing algorithm can find a new route for the packets.
    • WiFi
      • WiFi uses wireless radio frequencies.
      • These are normally 2.4GHz and 5GHz wavebands.
      • The waveband is split into many channels.
      • Has a range of about 20 meters.
      • Security is an issue.
    • Encryption
      • Due to the vulnerability of many networks, we need to protect the messages we send.
      • Encryption is the transmission of a message so that it can only be understood by who we want to read it.
      • Two keys called the public key and private key are used to encrypt messages.
      • The public key can be used by anyone and the private key is kept secret and is used to decode.
    • Protocols
      • Almost everything on the internet uses protocols.
      • Network addressing is getting a message from one computer to another.
      • The main one uses MAC and IP addressing.
      • IPv4 uses 4 groups of numbers. There can be just over 4 billion combinations.
      • Because we are running out of IPv4 addresses, we now use IPv6 which has more combinations.
      • IP addresses can be static or temporary. Static addresses never change.
      • The MAC address is unique to the network card and can be used to track any device on the internet.
      • Protocols and Standards
        • HTML - Hypertext mark-up language - writing web pages for display.
        • XML - Extensible mark-up language - A text-based means of describing data.
        • HTTP - Hypertext transfer protocol - for requesting and receiving HTML files.
        • HTTPS - Hypertext transfer protocol secure - for requesting and receiving HTML files over a secure encrypted connection.
        • CSS - Cascading office protocol - define how HTML elements are to be displayed.
        • POP - Post office protocol - for retrieving emails from a remote server.
        • IMAP - Internet message access protocol - allows complete management of a remote mailbox.
        • SMTP - Simple mail transfer protocol - This is the old standard for the transmission of email.
        • FTP - File transfer protocol - This is used to send computer files from one host to another.
    • Layering
      • Layering is used to split up tasks of a program which makes it easier to find an error had there happen to be one.
      • TCP/IP is used to define how to transfer data through a network.
      • TCP/IP stack: Layer 1: Application Layer 2: Transport Layer 3: Internet  Layer 4: Network
      • Packet Switching
        • The sending computer splits data into equal packets and each packet is given an address. Each packet gets error checking data and are then sent across the network.
        • The receiving computer checks to see if all the packets have been received. Packets are checked for errors.


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