unit 5:communication

networks
1. LAN
  1. A Local Area network is a network confined to one location or organisation.
2. WAN
  1. A Wide Area Network is a network of LANS spanning a wide area-for example the internet .
3. a network is a group of computers connected together so they can communicate
  1. advantages
    1. share files
    2. share resources (printer)
    3. provide a simple username password
  2. disadvantages
    1. expensive(extra part needed)
    2. lots of reasources
    3. security-can access all computers from one persons error
Topology
1. Bus Topology
  1. advantages
    1. cheap
    2. easy to install
    3. no extra equipment required
  2. disadvantages
    1. high chance of collision
    2. more computers mean more collisions
    3. damage to the wire results in catasrofic failure
2. ring topology
  1. advantages
    1. no collisions
    2. number of computers don't effect the speed
  2. disadvantages
    1. one faulty cable or faulty computer will result in a atrophic failure
    2. more difficulty to add new computers
3. star topology
  1. advantages
    1. no collisions
    2. failure of a cable or computer is not catastrophic
    3. easy to add new computers
  2. disadvantages
    1. expensive (requires hub/swithc and lots of cabling)
    2. failure of hub/switch is catrastrophic and difficult/ expensive to fix
4. mesh topology
  1. advantages
    1. almost impossible to break
  2. disadvantages
    1. very complex as route finding is necessary to decide path for data
    2. many redundant connection that are rarely used
path finding
1. circuit switching
  1. advantages
    1. data arrives in the order it was sent
    2. constant speed
    3. can start reading transmission as soon s first bit arrives as data arrives sequentially
  2. disadvantages
    1. only one transmission
2. packet switching
  1. advantages
    1. multiple transmissions can happen simultaneously
    2. large transmissions don't clog the network
  2. disadvantages
    1. a bit of lag
      1. is needed to allow several packets to arrive before reading as the first packet sent may not be the first packet received
3. routing
  1. a cost is assigned to each connection in a mesh
  2. route finding algorithms are used to find the lowest cost route between two nodes
network hardware
1. switch
  1. a switch routes packets round a network by analysing them and sending them to the device they are addressed to.
2. hub
  1. a hub routes packets round a network by blindly sending them to every device its connected to.
3. bridge
  1. bridge connects together two networks that use the same base protocals
4. gateway
  1. a gateway connects together two networks that use different base protocals
5. router
  1. a router stores the addresses of computers on its network and treansfers their data to devices on other networks
6. WAP
  1. a WAP is a device that creates a wireless network and allows other devices to connect
7. NIC
  1. a NIC is a device that joins the network(wired or not) and connects to a computer or other devices

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