WJEC Data Transmissions

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What is bandwith?
Not a measure of speed, but how much data can be placed onto a cable at any point in time.
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What is simplex?
Data transmission is possible in one direction.
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What is half-duplex?
Data transmission is possible in both directions, but only direction at a time.
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What is full duplex?
Data transmission is possible in both directions simultaneously.
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Why is digital preferred over analogue?
Digital is less likely to suffer corruption/interference
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Why would a computer need to use analogue digital?
Some input devices produce an analogue signal, eg: microphone
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What is switching?
Prevents all data from being sent to all parts of a network.
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Why use switching?
It's efficient to not send data where it is not needed.
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Data transfer rate. Transfer is 3MBPS, How long for 5MB?
13.98 Seconds. 5 x 1024 x 1024 (Convert into MB) = 5242880 X 8 (Convert into 8 bit) = 41943040 / (1000 x 1000) MB = 41.94 MB Divide this answer by 3 41.94/3 = 13.98 Seconds
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How does Time division multiplexing work?
Transmission is split into very small time slices which a number of bytes from each process transmit per time slice.
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What type of technology is time division multiplexing?
Digital Technology
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What type of technology is frequency divison multiplexing?
Analogue Technology
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What is handshaking?
Handshaking takes place in order to establish rules for communication when a computer sets about communicating with another foreign computer.
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Describe the process of circuit switching
Circuit switching is where a path is set up between the sender and the receiver before the start of transmission and is kept open until the end of transmission. All data follows the same path in order. The path cannot be used by any other data.
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Give some advantages and disadvantages of circuit switching
Can't transmit any other data as the path is dedicated. No waiting for message to arrive as there is no delay. Suitable for long continuous transmission. Data path receives guaranteed data path.
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Describe the process of packet switching
Is where the data is split into packets before transmission. Each packet may be transported by different routes through the network. They may arrive out of order but will reassemble on arrival.
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What is in a data packet?
The data packet contains the order number, source and destination address, error and control signals.
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Give some advantages and disadvantages of packet switching
More efficient use of data lines and less waiting between gaps. Cheaper as doesn't require hiring particular path. Better security as packets cannot be intercepts or reconstructed. Network failure not important as packets can take alternative routes.
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PART 2 of advantages and disadvantages of packet switching
More processing as packets are reassembled.
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Calculating route costs
Packet needs to be sent from A to B. Sending directly has a cost of 6 but sending via C = 5 therefore this is the desired path
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What is column names are in a calculating route table?
Destination Cost Go To
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What is a router?
A router connects together many different segments. A router is a device that holds information about the addresses of the computers in a network and can direct data to the correct computer
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What do routers do?
It recieves packets from one segment and is able to pass it on to other connected routers or segments.
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What happens if there is only one segment in a network with many workstations?
There will be heavy data traffic and this will slow down the system unacceptably.
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What do routing devices do to avoid this?
They will maintain routing tables to calculate the best route for a data packet.
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What is multiplexing?
Multiplexing is where several independent data sources are combined to be sent along a single route to a single destination.
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Where is multiplexing used?
Telecommunications and electronics
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What is a protocol?
Is a set of rules to specify data formats for computers to communicate with each other
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What does a protocol include?
Includes physical connections such as data transfer speed, data format, error detection, correction methods
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What is a data collision?
Is where two sets of data in the same network are transmitted simultaneously
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What does the network do when a data collision occurs?
The network detect s an error and each computer will wait a random time until they send data again
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What is serial transmission?
Data is sent bit by bit down same data line
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Advantages and disadvantages of serial transmission
Requires only two wires therefore its cheaper. Serial can travel longer distance. Simpler interface
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What is parallel transmission?
Bits in a byte sent simultaneously along separate lines
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Advantages and disadvantages of parallel transmission
Requires 8/16 wires so more expensive and there are more pins integrated on the board. Transmission superficially faster than parallel transmission. Cross talk interference can corrupt data. Wider bus means more data
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What does TCP/IP stand for?
Transmission Control Protocol/Internet Protocol
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What does tcp do?
Enables two hosts to establish a connection
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What does ip do?
Deals only with sending the packets
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What is TCP?
One of the main protocols in networks
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What does TCP guarnetee?
The delivery of data and delivered data.
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What is the process of TCP?
TCP uses a 3-way handshake to initiate a transfer. TCP splits files into segments. Sender sends packets. Receiver sends acknowledgement when received. More packets are sent, sender keeps records of packets sent. Sender times when packet sent and
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Part 2 Process of TCP
re transmits if timer expired. TCP at receiver reassembles.
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What does DHCP do?
s a client/server protocol that automatically provides an Internet Protocol (IP) host with its IP address
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Other cards in this set

Card 2

Front

What is simplex?

Back

Data transmission is possible in one direction.

Card 3

Front

What is half-duplex?

Back

Preview of the front of card 3

Card 4

Front

What is full duplex?

Back

Preview of the front of card 4

Card 5

Front

Why is digital preferred over analogue?

Back

Preview of the front of card 5
View more cards

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