Topic 2 test Flashcards
Data sent over long distances is usually broken up into what?
data packets (sometimes called datagrams)
How large are the packets of data (typically)?
64 KiB
Why are packets of data usually quite small?
Because they are easier to control than a kong continuous stream of data
What does this idea of splitting up data mean?
That each packet can be sent along a different route to its destination (very useful when some rout is out of action or busy)
A drawback of splitting data into packets is?
The need to reassemble the data when it reaches its destination.
What is a typical packet split up into?
A packet header, the payload, a trailer
What does the packet header consist of?
- IP address of the sending device
- IP of the receiving device
- sequence number of the packet (to make sure packets can be reassembled correctly)
- packet size
NOTE: another value indicating how many there are total in the transmission
What does the payload consist of?
The actual data being sent in the packets (around 64 KiB of data)
What does the trailer consist of?
- some way of identifying the end of the packet
- error checking method called CRC (cyclic redundancy checks)
What is packet switching?
a method of data transmission where a message is broken up into a number of packets
benefits of packet switching?
- no need to tie up a single communication line
- possible to overcome failed for faulty lines by re-routing packets
- easy to expand package usage
- high data transmission rate is possible
Drawbacks of packet switching?
- packets can be lost and need to be resent
- prone to errors with real time streaming
- delay at the destination while packets are being re-ordered
What can data transmission cover?
Short distance (computer to printer)
Long distance (0ver the internet)
What are the factors that need to be considered when transmitting data?
- direction of data transmission
- method of transmission
method of synchronization between the two devices
What is simplex?
data transmission going in one direction only (computer to printer)
What is half-duplex?
Data transmission in both directions but not at the same time (walkie talkie)
What is full-duplex?
Data transmission is in both directions art the same time (simultaneously) - telephone conversation
What is serial data transmission?
when data is sent, one bit at a time, over a single wire or channel
facts about serial data transmission?
- works well over long distances
- data is transmitted at a slower rate than parallel data
What is parallel data transmission?
when several bits of data are sent down several wires or channels at the same time
facts about parallel data transmission/
- one wire or channel is used to transmit each bit
- works well over short distances
When are parallel and serial used?
serial: USB (Universal Serial Bus)
parallel: Internal computer components, pathways between memory and CPU
facts about USB?
- most commonly used type of input/output
- allows both half-duplex and full-duplex data transmission
What does the USB consist of?
4 wired shielded cables
- white and green are used for data transmission
Benefits and drawbacks of USB?
benefits:
- become an industry standard
- supports different data transmissions ates
- is backward compatible
drawbacks:
- standard USB only supports a maximum cable length of 5m
what is USB-C?
a new type of USB connector
- becoming more common in laptops and computers/phones
what is asynchronous data transmission?
- refers to data transmitted in an agreed bit pattern
- bits are grouped together and sent with CONTROL BITS
- prevents data being mixed up
- makes it possible to separate groups of data
what is synchronous data transmission?
- continuous stream of data
- ensures the sender and receiver are synchronized
- faster data transfer method than asynchronous
Is USB asynchronous or synchronous?
it is asynchronous
