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Data Transmissions, Error detection - Coggle Diagram
Data Transmissions
Packet switching
Tie up a single communication line
Busy faulty lines.
Package usage
High transmission
Lost - resent
Prone to errors
Delay
Packets
Header ( IP addreses of both sides)
Payload ( 64 KiB Data is stored here)
Trailor ( Error checking )
simplex. half duplex full deplex
Simplex: One direction only.
Half duplex: 2 directions but not at the same time
Full duplex: Same ways at the same time
Serial data transmission
1bit at a time over single wire/channel
work well over long distances
slower rate compared to parallel
Parallel
Transfer several bits of data at the same time/ several channels several wires
Fast
unable to send data over long distances ( 20m )
Universal serial bus ( USB )
Serial data
half duplex and full duplex
Red (5V+)
White(data + )
Green ( data - )
Black ( ground )
Pros
Automatically detected
Can support diff data trans rates
Industry standard
Error free
Cons
5m wire length maximum
Not all new computers support usb
slower trans rate
Hopping
Maximum hop number
Missing detected: Send signal - Resend packet
Error detection
Echo check
Data sent to another device
Another copy of data sent to sender
Correct
Wrong ( Resend )
Checksum
Checker at the end of each byte
agreed algorhitm
If same ( data is good )
Different ( resent )
Check digits
Final digit in a code
Calculate all the other digits in that code
=> Which number is wrong => correct number is:
Why?
When data is transmitted
Corrupted, lost or gained
Parity checks
Whether data has been changed or corrupted
count the number of 1s in a byte
Parity even/odd
odd ( odd number of 1s)
Even ( even number of 1s)
ARQ
Acknowledgements
Positive ( good data )
Negative ( Bad Data )
Timeout ( Time interval taken before acknowledgement is recieved )