Communication

Communication

1. Topologies

   • Ring
     • Advantages
       • No chance of data collision
     • Disadvantages
       • Still high chance of catastrophic failure if one device goes down
   • Star
     • Advantages
       • No data collision, reliable network, no catastrophic failure if cables fail
     • Disadvantages
       • Expensive hub/switch, if it goes down, network goes down
   • Bus
     • Advantages
       • Cheap and easy to set up
     • Disadvantages
       • Incredibly high chance of data collision, and catastrophic failure of cable
   • Mesh
     • Circuit Switching
       • Path across network established
         • Is locked for duration of communication
     • Packet Switching
       • Data split into packets, sent independently usually using different paths.
         • Packets usually arrive out of order, lag required to reassemble data.
     • Routing
       • Before transmitting, a route has to be decided.
         • To do this, each node tests its connections, assigning a cost to them.
           • Pathfinding algorithms are used to evaluate cost, in order to find the least costly path to the recipient.
     • Advantages
       • Very little risk of catastrophic failure
       • Disadvantages
         • High cost to set up, setting this type of network is also incredibly difficult

2. Wireless Network

   • Network where computers use radio waves with no physical connection to communicate
     • Wi-Fi
     • Bluetooth

3. Wired Network

   • A network where computers communicate via cable
     • Ethernet

4. LAN

   • A network that is contained within a single organisation or covers a small geographical area
     • Example: A Wi-Fi network in a house

5. WAN

   • Network that covers multiple organisations or covers a large geographical area.
     • Example: A company's network spanning multiple buildings

6. TCP/IP Layers

   • Physical Layer
     • Data Link Layer
       • Network Layer
         • Transport Layer
           • Application Layer
             • Group of applications requiring network communication
           • Establishes connection between applications on different hosts
         • Responsible for creating frames that move across network
       • Responsible for creating frames that move across network
     • Transceiver that drives signals on network

7. DNS

   • When you type in a web address into a browser, DNS server returns IP address
   • Stands for Domain Name Server

8. Internet Protocol

   • Version 4
     • ~4 Billion IP Addresses (32-bits)
       • Not Enough
   • Version 6
     • 48 bit, many more IP Addresses possible
       • Enough for now