AQA Alevel UNIT 4.9 Networking

AQA Alevel UNIT 4.9 Networking

1. Communication

   • TRANSMISSIONS
     • Parallel Transmission
       • Advantages
         • Faster, as more bits are transferred per cycle
       • Disadvantages
         • Less reliable over long distances
         • more expensive - more wiring needed
       • Parallel transmission sends each bit at the same time, each along its own channel
     • Serial Transmissions
       • Advantages
         • Cheaper to produce the hardware
         • Easy to set up
         • Works well over long distances
         • Wires less bulky
       • Disadvantages
         • Only one bit per cycle
       • Serial transmission sends each bit along the same channel, one after another
     • Synchronous Transmission
     • Asynchronous Transmission
     • Latency
       • Latency is the delay between the start of the transmissions and the start of the effect of transmission
       • For transmitting data, its the time taken for the first bit to be recieved
     • Protocols
     • Rates
       • Bitrate
         • is one of the main measures of digital trnasmission
         • it is simply the number of bits transferred in a specific time.
       • Baud
         • refers to the mechanical properties of the analogue wires for digital transmission
         • it is the number of signal changes per second that the wire can handle without the signal being garbld
       • Bandwidth
         • Is the potential capacity of the transmission channel

2. Network Topologies

   • The three Common
     • Bus
       • A single wire connects all computers
         • All clients and servers connect to this cable
       • Advantages
         • Cheap
         • Easy to install
         • No extra equipment required
       • Disadvantages
         • Only suitable for small networks
         • Faukts are catastrophic (could take the entire netowrk down
     • Ring
       • Similar to bus network but the computers are connected in a ring
       • All communication goes one way
       • Advantages
         • Cheap
         • Easy to install
         • No extra equipment required
         • Fewer collisions than bus topology
       • Disadvantages
         • Faults are still catastrophic
         • Difficult to add new nodes/computers
     • Star
       • All nodes/computers are connected to a central hub
       • Hub directs all traffic to appropriate nodes
       • Advantages
         • Reliable and fast
         • Easy to add new nodes/computers
         • One fault doesn't take the whole network unless the hub was to go down
       • Disadvantages
         • Expensive
         • Requires Hub and a lot of cabling
         • Hub requires maintenance
   • Physical v Logical
     • Modern networks are almost always Star topologies – a central switch or router connected to each computer.
     • Logically, however, they behave as bus networks. Each computer on the network can see each other, and can communicate directly.
     • By using bus protocols, and a switch that manages the connections, each computer will see the network as a bus network, and won’t need to communicate directly with the switch.
   • Network Types
     • Client-server
       • Computers have different roles. Servers exist to perform specific task
         • Such as: File Distribution, Internet distribution, Printer management, web-page distribution.
         • Clients request
         • Servers constantly respond or check for request
     • Peer-to-peer
       • Communism
         • All computers have equal status, there are no servers
         • The load is distributed amongst the network so no powerful server is needed
       • Great for distribution of files
       • Not database driven as computers could get out of sync with each other as one node updates differently to another

3. KEY

   • Discription
     • Simplified discription
     • is it mainly used or not
   • pros
   • Cons