Networks Flashcards
Define Serial data transmission
when bits are sent one after another along the same data line
Define Parallel data transmission
several bits are sent simultaneously along separate lines or channels
what is skew and how is it caused
it is when data arrives unsynchronised , as each individual wire has slightly different properties bits travel at slightly different speeds along each of the wires
what is crosstalk and its problems
it refers to electromagnetic interference between two adjacent channels or parallel wires. It gets more pronounced as the frequency increases.
What type of transmission is preferred for long distances
serial transmission is reliable over very long distances at very high data transfer rates (frequencies)
At what distance can parallel transmission be used up to?
around 2m due to crosstalk
what is an example of a serial connector and its benefit
USB connecters are much smaller and cheaper than parallel connectors
define synchronous data transmission
all data transfers are timed to coincide with an internal clock pulse.
How is Data sent using synchronous transmission
- The data is sent as one long stream with no gaps in transmission
- The receiver counts the bits and reconstructs bytes
Define asynchronous data transmission
each byte is sent seperately the moment it is available instead of waiting for a clock signal
How are bytes sent in asynchronous transmission
each byte is preceded by a start bit and ends with a stop bit or stop period - a short time gap between each set of bits
what is a parity bit
it is added as the 8th bit as a form of error detection, this bit is set to a 1 or 0 to make the total number of 1’s or 0’s in each byte odd or even depending on the machine
disadvantages and advantages to asynchronous transmission
- relatively slow owing to the increased number of bits sent
* it is a cheap and effective form of serial transmission suited to low speed connections like a KnM
Define Latency
It is the time delay between the moment the first byte or packet of a communication starts and when it is received at its destination
Define protocol
The set of rules relating to communication between devices, all communications between devices require the devices agree on a format of the data.
what things do the protocol need to define
- standards of physical connections
- rate of transmission
- data format
- type of transmission a/synchronous
- error checking procedures
Define bit rate
the number of bits transmitted in one second over a wired or wireless data link
Define Baud rate
the rate at which the signal in a communications channel changes state
What is a baseband, and how are bits sent along it.
it carries one signal at a time, a bit is represented by a high or low voltage in the cable
Define Broadband
it carries multiple signals on a fixed carrier wave. bits are sent as variations on the wave
what is the formula for bit rate
bit rate = baud rate x number of bits per signal
Define Bandwidth
it is a measure of the maximum capacity of a communications channel
Define Local Area Network
two or more computers connected together within a small geographical area