unit 5:communication

unit 5:communication

1. networks

   • LAN
     • A Local Area network is a network confined to one location or organisation.
   • WAN
     • A Wide Area Network is a network of LANS spanning a wide area-for example the internet .
   • a network is a group of computers connected together so they can communicate
     • advantages
       • share files
       • share resources (printer)
       • provide a simple username password
     • disadvantages
       • expensive(extra part needed)
       • lots of reasources
       • security-can access all computers from one persons error

2. Topology

   • Bus Topology
     • advantages
       • cheap
       • easy to install
       • no extra equipment required
     • disadvantages
       • high chance of collision
       • more computers mean more collisions
       • damage to the wire results in catasrofic failure
   • ring topology
     • advantages
       • no collisions
       • number of computers don't effect the speed
     • disadvantages
       • one faulty cable or faulty computer will result in a atrophic failure
       • more difficulty to add new computers
   • star topology
     • advantages
       • no collisions
       • failure of a cable or computer is not catastrophic
       • easy to add new computers
     • disadvantages
       • expensive (requires hub/swithc and lots of cabling)
       • failure of hub/switch is catrastrophic and difficult/ expensive to fix
   • mesh topology
     • advantages
       • almost impossible to break
     • disadvantages
       • very complex as route finding is necessary to decide path for data
       • many redundant connection that are rarely used

3. path finding

   • circuit switching
     • advantages
       • data arrives in the order it was sent
       • constant speed
       • can start reading transmission as soon s first bit arrives as data arrives sequentially
     • disadvantages
       • only one transmission
   • packet switching
     • advantages
       • multiple transmissions can happen simultaneously
       • large transmissions don't clog the network
     • disadvantages
       • a bit of lag
         • is needed to allow several packets to arrive before reading as the first packet sent may not be the first packet received
   • routing
     • a cost is assigned to each connection in a mesh
     • route finding algorithms are used to find the lowest cost route between two nodes

4. network hardware

   • switch
     • a switch routes packets round a network by analysing them and sending them to the device they are addressed to.
   • hub
     • a hub routes packets round a network by blindly sending them to every device its connected to.
   • bridge
     • bridge connects together two networks that use the same base protocals
   • gateway
     • a gateway connects together two networks that use different base protocals
   • router
     • a router stores the addresses of computers on its network and treansfers their data to devices on other networks
   • WAP
     • a WAP is a device that creates a wireless network and allows other devices to connect
   • NIC
     • a NIC is a device that joins the network(wired or not) and connects to a computer or other devices

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