Computing - Communication
See Also:
Serial vs Parallel
What is serial data transmission?
Where bits are sent one after another along the same data line.
How can you do two-way communication using serial data transmission if you only had one wire?
You would need two wires.
What’s an example of a serial data cable?
USB
How are serial cables sometimes deceptive in their ability to do two-way communication?
The multiple data lines are sheathed together so it only looks like one line.
What is parallel data transmission?
Several bits are sent simultaneously along seperate data lines.
How can you do two-way communication using parallel data transmission?
You would need twice the number of wires.
What’s an example of a parallel data cable?
A cable connected to a printer.
In one word, what is the main issue with parallel data transmission?
Skew.
In parallel data transmission, what is skew?
Where bits travel at slightly different speeds along each line.
Why is skew an issue in parallel data transmission?
All the bits will arrive at slightly different times.
What phenonemon does this photo show?
What phenonemon does this photo show?Skew.
When does skew get worse?
When the cables are longer.
What is crosstalk?
Electromagnetic interferences between two parallel data lines or wires.
When does crosstalk get worse?
When the speed of transmission increases.
When can you use parallel data trasmission?
Over very short distances.
What’s the maximum distance you can use parallel data transmission over?
About $2m$.
When can you use serial data transmission?
Over very long distances.
Why is serial transmission more reliable than parallel transmission?
You don’t get skew or crosstalk issues.
What is smaller and cheaper: serial cables or parallel cables?
Serial cables.
Asynchronous vs Synchronous
What is synchronous data transmission?
Where all data transfers are timed to coincide with an internal clock pulse.
Is this synchronous or asynchronous data transmission?
Is this synchronous or asynchronous data transmission?Synchronous.
What is asynchronous data transmission?
Where each byte is sent separately the moment it is available instead of waiting for a clock signal.
In asynchronous data transmission, what is each byte preceeded with?
A start bit.
In asynchronous data transmission, what is each byte preprended with?
A stop bit or a stop period.
Is this synchronous or asynchronous data transmission?
Is this synchronous or asynchronous data transmission?Asynchronous.
In asynchronous data transmission, how are the bits verified?
Using parity bits.
Why is synchronous data transmission sometimes considered slow?
Because you have to wait for the clock.
Why is asynchronous data transmission sometimes considered slow?
Because you have to send additional stop and start bits.
Does a keyboard or mouse use synchronous or asynchronous data transmission?
Asynchronous.
Latency
What is latency?
The time delay between the moment the first byte or packet of a communication starts and when it is received at its destination.
Speed of Transmission
What is bit rate?
In [[Computing - Networking]]A
What is baseband?
Where you have a high and low voltage which represents a $1$ and $0$.
What method of transmission does this show?
What method of transmission does this show?Baseband.
In baseband, what is the speed of signal change directly proportional to?
The bit rate.
What is baud rate?
The rate at which the signal in a communications channel changes state.
If in baseband transmission, if the baud rate is $1,000,000$ signal changes per second, what is the bit rate?
$1,000,000$ bits per second.
What’s the relationship between bit rate and baud rate?
They are the same.
What is broadband?
Where multiple signals are sent as variations on the wave.
What method of transmission does this show?
What method of transmission does this show?Broadband.
If you have 4 different voltages on a carrier wave, how many bits can you send with each signal change?
What’s the relationship between bit rate and baud rate here?
What’s the relationship between bit rate and baud rate here?Baud rate is twice the bit rate.
What is the formula for bit rate in terms of baud rate?
If a signal changes at a million times a second and $8$ bits are encoded on each signal, what is the bit rate?
If a signal changes at a million times a second and $8$ bits are encoded on each signal, what is the baud rate?
What does even parity mean?
Add a $1$ or a $0$ to make the total number of $1$s an even number.
What does odd parity mean?
Add a $1$ or a $0$ to make the total number of $0$s an odd number.
What is a stop bit equal to?
What is a start bit equal to?
What’s different about stop and start bits to how you would expect?
They go the other way around, stop bits come first, followed by a start bit.
2021-02-02
How would you describe this network?
How would you describe this network?A peer-to-peer network.
What is a server?
A computer that provides services or resources required by any of the clients.
What is a client?
A computer which requests serivces or resources provided by the server.
In networking, what is a terminal?
Clients of a central server.
What are some examples of specialised servers?
- Web server
- Print server
- Mail server
- File server
- Database server
Why are peer-to-peer networks not as secure?
Because if one machine is a weak link then the whole network is insecure.
What kind of organisation would a peer-to-peer network be useful for?
Small companies with fewer computers.
Which is cheaper: client-server networks or peer-to-peer networks?
Peer-to-peer networks.
Which is more restrictive/secure: client-server networks or peer-to-peer networks?
Client-server networks.
How could you describe each node of a peer-to-peer network in terms of a client-server architechture?
Each node can act as both a client and a server.
What is the main use of peer-to-peer networks?
File-sharing.
Why are peer-to-peer networks used for pirating?
They are hard to shut down.