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Fundamentals of communication
and networking
Last edited time @October 1, 2023 10:45 AM
Status Done
Communication basics
Transmission
Serial and Parallel transmission
Serial transmission → data is sent down a single wire one bit at a time. This
means that data is transmitted in the order it is received. Serial tranmission
can be very quick.
Parallel transmission → data is sent down multiple wires at a time. This is
means that multiple bits can be transmitted down the cable at a single time.
The more wires there are the more data that can be sent at once.
Some problems with parallel cables include:
More expensive to produce
The signal will also degrade as distance or speed increases due to
interference between the lines.
Timing the signals so that they are received at the same time and in
sequence. This is known as synchronisation and becomes more
difficult as the number of lines increases.
Synchronous and Asynchronous data transmission
Synchronous data transmission → Data is transmitted where the pulse of the
clock of the sending device and receiving device are in time. The 2 devices may
share a single clock.
Allows for more data to be transmitted at once because every bit is used
for the data.
Fundamentals of communication and networking 1
, Asynchronous data transmission → Data is transmitted between two devices
that do not share a common clock signal. The sending and recieving devices
synchronise only for the portion of the transmission.
❗ It should be noted that the number of bits being sent, the type of
parity being used and the number of stop bits being used in the
transmission is already agreed upon by the 2 devices.
The 2 devices synchronise using start and stop bits. A parity bit is also
used.
Start bit → A bit used to indicate the start of transmission.
Stop bit → A bit used to indicate the end of transmission,
Parity bit → A method of checking binary codes by counting the
number of 0s and 1s in the code. 🔒 Fundamentals of Data
representation
Asynchronous transmission is slower as some of the bit capacity is taken
up by the start and stop bits.
Fundamentals of communication and networking 2
, Bit rate, Baud rate, Bandwidth and Latency
Bit rate → The number of bits that are being received on each electronic state in the
wire.
Baud rate → The number of electronic state changes per second.
Bandwidth → The range of frequencies that are available on the transport medium. It
is a measure of the capacity of the channel. It is measured in Hertz [Hz].
Latency → The time delay that occurs when transmitting data between devices.
There are 3 general causes of latency when communicating data.
Propagation latency → The amount of time it takes for a logic gate within a
circuit to transmit the data.
Transmission latency → The amount of time it takes to pass through a
particular communication medium, for example, fibre optic would have a
lower latency than copper cable.
Processing latency → The amount of time it takes data to pass around a
network depending on how many servers or devices it has to pass through.
To measure latency you would use a ping test.
It works by sending an item to a point on the network and measuring how
long it takes to come back (be received by the sender).
Protocols
Protocols → They are a set of rules that govern how computers can communicate with
each other. They cover aspects such as the format in which data should be transmitted
and how the items are identified.
Networks
Fundamentals of communication and networking 3
Fundamentals of communication
and networking
Last edited time @October 1, 2023 10:45 AM
Status Done
Communication basics
Transmission
Serial and Parallel transmission
Serial transmission → data is sent down a single wire one bit at a time. This
means that data is transmitted in the order it is received. Serial tranmission
can be very quick.
Parallel transmission → data is sent down multiple wires at a time. This is
means that multiple bits can be transmitted down the cable at a single time.
The more wires there are the more data that can be sent at once.
Some problems with parallel cables include:
More expensive to produce
The signal will also degrade as distance or speed increases due to
interference between the lines.
Timing the signals so that they are received at the same time and in
sequence. This is known as synchronisation and becomes more
difficult as the number of lines increases.
Synchronous and Asynchronous data transmission
Synchronous data transmission → Data is transmitted where the pulse of the
clock of the sending device and receiving device are in time. The 2 devices may
share a single clock.
Allows for more data to be transmitted at once because every bit is used
for the data.
Fundamentals of communication and networking 1
, Asynchronous data transmission → Data is transmitted between two devices
that do not share a common clock signal. The sending and recieving devices
synchronise only for the portion of the transmission.
❗ It should be noted that the number of bits being sent, the type of
parity being used and the number of stop bits being used in the
transmission is already agreed upon by the 2 devices.
The 2 devices synchronise using start and stop bits. A parity bit is also
used.
Start bit → A bit used to indicate the start of transmission.
Stop bit → A bit used to indicate the end of transmission,
Parity bit → A method of checking binary codes by counting the
number of 0s and 1s in the code. 🔒 Fundamentals of Data
representation
Asynchronous transmission is slower as some of the bit capacity is taken
up by the start and stop bits.
Fundamentals of communication and networking 2
, Bit rate, Baud rate, Bandwidth and Latency
Bit rate → The number of bits that are being received on each electronic state in the
wire.
Baud rate → The number of electronic state changes per second.
Bandwidth → The range of frequencies that are available on the transport medium. It
is a measure of the capacity of the channel. It is measured in Hertz [Hz].
Latency → The time delay that occurs when transmitting data between devices.
There are 3 general causes of latency when communicating data.
Propagation latency → The amount of time it takes for a logic gate within a
circuit to transmit the data.
Transmission latency → The amount of time it takes to pass through a
particular communication medium, for example, fibre optic would have a
lower latency than copper cable.
Processing latency → The amount of time it takes data to pass around a
network depending on how many servers or devices it has to pass through.
To measure latency you would use a ping test.
It works by sending an item to a point on the network and measuring how
long it takes to come back (be received by the sender).
Protocols
Protocols → They are a set of rules that govern how computers can communicate with
each other. They cover aspects such as the format in which data should be transmitted
and how the items are identified.
Networks
Fundamentals of communication and networking 3
