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Local Area Network (LAN)
- machines are close together
- connected together using cables or wireless
- data is more secure
- high data transfer rates
- e.g. in schools, at home
- hardware: fibre optics, network interface card, server
- software: network operation system
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Wide Area Network (WAN)
- spread more remotely
- uses communication system
- long distance communication technologies
- e.g. the internet
- hardware: modem, router
- software: browser, firewall
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Data transmission: serial
send the byte, one bit at a time, through a single wire
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Data transmission: parallel
uses a number of wires, one for each of the bits in the byte
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Data transmission: simplex
one way data communication
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Data transmission: half-duplex
data can only be sent in one direction at a given time
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Data transmission: duplex
bidirectional data communication
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Time sensitivity
- more wires connecting devices, the more data that can be transmitted in a given period of time
- bit rate- number of bits that can be transmitted within a timeframe, measured in baud
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Echoing back
- send data back to the sending device
- compares the data to what was sent
- if they match it is OK
- if different, the data is sent again
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Check sums
- data sent is made up of binary numbers
- original bytes added together and answer sent with data
- when reached destination checksum is worked out
- if numbers are differnet the data is resent
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Parity check
- data sent is in fixed bytes
- eighth bit as parity bit
- number of 1's have to be the same after as before
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Packet switching
- transmission across a network
- groups data
- packets sent any route
- packets have to be rearranged
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Circuit switching
- uses a dedicated route
- very fast rates
- packets sent along in order
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Protocol
- a set of rules that govern the transmission of data
- Handshake Signal: Sent from one device and acknowledged by the other. This states that both are now ready for communication. Unless both device follow the same rules, there can be no connection
- Logical: Baud Rate (Compression type), Error correcting technique (file type), Routing (packet size), Flow Control, Synchronisation, Rules governing data
- Physical: wired, and data can be transferred by either serial or parallel transmission. The data transmission will have different frequencies depending on whether it is wireless or wired.
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