2.2 Data Transmission Flashcards
What is serial transmission?
Data is sent bit-by-bit along the same data line.
What are 3 advantages of serial transmission?
Only requires 2 wires instead of 8 or 16 in parallel.
Serial can travel longer distances.
Serial has a more simple interface.
What is a disadvantage of serial transmission?
It is much slower than parallel.
What is parallel transmission?
All bits in a byte are sent simultaneously along separate lines.
What is an advantage of parallel transmission?
It is much faster than serial transmission.
What is a disadvantage of parallel transmission?
It cannot be used over as long a distance as serial (Due to interference along the cable)
What is a Simplex data transmission process?
Where data transmission is possible in one direction only.
What is a Half-Duplex data transmission process?
Where data transmission is possible in both directions but only in one direction at a time.
What is a Full-Duplex data transmission process?
Where data transmission is possible in both directions simultaneously.
What are 3 reasons for transmitting data digitally?
It is less likely to suffer corruption/degradation/interference.
It is possible to error check the data.
Can compress data therefore the transfer time is quicker.
What is multiplexing?
It is where several independent data sources are combined to be sent along a single route to a single destination.
A multiplexor allows messages to be combined so they can be sent simultaneously and then separated again at the end of the link.
What is Time Division Multiplexing?
Allocates small time slices alternately for data from each of the input message streams.
What is Frequency Division Multiplexing?
Sends the messages simultaneously but uses different transmission frequencies.
What is Switching?
Switching prevents all data being sent to all parts of a network and makes efficient use of the data lines.
What is Circuit Switching?
A path is set up between sender and receiver and is released after transmission is complete.
Data is sent in order and cannot be used by any other traffic during that time.
What is Packet Switching?
Data is split into packets which can take a different route through a network and may arrive out of order.
This means it is then re-assembled into the correct order.
What does each packet carry during Packet Switching?
The actual data.
The order number of the packet.
Source and destination addresses.
Control signals.
Error control bits.
Why is Packet Switching preferred?
It has better security as it can’t be intercepted.
It involves more efficient use of the data lines.
Less likely to be affected by a network failure.
What is a switch?
It is used to connect computers in a local area network.
The switch is programmed with a table including IP address of all connected devices so data can be sent to the required device.
Packets of data are received and checked to determination the destination address.
What is a router?
A router is used to forward data packets between networks and control traffic on wider area networks such as the internet.
It determines the destination of a data packet from the IP address and then selects an appropriate route for onwards transmission (Fastest Path).
How can a data collision occur on a network?
When two sets of data are detected simultaneously on the network.
Each computer will then wait for a short time and send the data again.
What is bandwidth?
It is a measure of how much data can be fitted onto a cable at any point in time.
Data still flows at the exact same speed.
What is The Internet?
A world-wide communications infrastructure of interconnected packet-switched networks.
Consists of a number of specialist hardware components such as routers and switches.
