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Year 11 - Computer Science notes
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- 1Unit 5Communication
- 2Networksa group of computers connected together so they can communicate
- 3Adv:+share files, so the same files are available whichever computer is used
+provide a single username and password that can be used on every computer on the network - 4Dis:-expensive- extra hardware needed
-more room for error- if something goes wrong it can affect every computer
-difficult- it requires a lot of technical expertise
-security issues more probable - 5LAN: Local Area Network-a network confined to one location or organisation
-its resources are only accessible by computers on that LAN - 6WAN: Wide Area Network-a network of LANs spanning a wide area
-the internet is an example of a WAN - 7Wired-connected with physical wires > electrical pulses used
-transmits binary data between computers/ the network - 8Wireless-radio-waves used
-no physical connection needed
-transmits binary data between computers/ the network - 9Topologies-four different ways we can connect computers into a network (Bus Topology, Ring Network, Star Network & Mesh Topology)
- 10Collisiontwo computers attempt to transmit on the same channel and the signals interfere and get corrupted, required them to try again
- 11Catastrophic Failurea severe fault prevents the entire network from functioning
- 12Bus Topology-a single cable connects all the computers
-all the clients and servers connect to this cable
-terminators are attached to each end of the cable - 13Adv & Dis:+Cheap +easy to use +no extra equipment required
-high chance of collisions -more computers means more collisions -damage to the wire results in catastrophic failure -only suitable for small networks - 14Ring Network-each computer is connected to two other computers in a ring formation
-each computer receives signals from one of its connected computers
-if the data is for itself, it reads it, if not it transmits it to the next computer
-the data travels around the ring in one direction until it reaches its intended recipient - 15Adv & Dis:+no collisions, as each cable only has one computer able to transmit on it
+number of computer does not
-one faulty cable or computer will result in catastrophic failure
-more difficult to add new computers - 16Star Network-all computers are connected to a central hub or switch
>a hub sends each message to all the other computers
>a switch checks the address and sends it only to the correct one - 17Adv & Dis:+no collisions +failure of a cable or computer is not catastrophic +easy to add new computers
-expensive (requires hub/ switch and lots of cabling) -failure of hub/ switch is catastrophic and difficult/ expensive to fix - 18Mesh Topology-each computer is connected to one or more other computers
- a full mesh has every computer connected to every other computer
- a partial mesh has only some of the computers connected - 19Adv & Dis:+zero catastrophic failure- there are always alternate paths for data +multiple transmissions can happen simultaneously
-redundancy- lots of unnecessary connections -expensive -difficult to maintain and administer - 20ways to navigate a mesh network-
- 21circuit switchinga path across the network is established - that path is locked and remains open for the duration of the communication
- 22Adv & Dis+data arrives in the order it was sent + data arrives at a consistent sped + can start reading transmission as soon as the first bit arrives, as data arrives sequentially
- only one transmission at a time along each channel - clogs the network - 23packet switchingthe data is split into lots of small chunks called packets - each one is sent independently, likely using different paths - the packets are re-assembled at the other side
- 24Adv & Dis+ multiple transmissions can happen simultaneously + large transmissions don't clog the network
-lag (a delay) is needed to allow several packets to arrive before reading, as the first packet sent may not be the first packet received - 25Routing- a cost is assigned to each connection in a mesh - route-finding algorithms are used to find the lowest cost route between two nodes
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- GCSE Computing Fichas sobre Year 11 - Computer Science notes, creado por Rebecca Hall el 02/09/2021.
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- Rebecca Hall
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