Did my Data Arrive Safely?
Computer Science: OCR A Level, topic 3.3.15
Did my Data Arrive Safely?
Interference across a network can cause data to become corrupted (changed) as it is transmitted to the recipient.
Lost packets
- Some packets might get lost within the network.
- Each packet transfer will have a certain timeout, which is the maximum amount of time that the packet transfer is expected to take.
- If the time taken is more than the timeout, then we send a timeout signal to the sender to ask them to re-send the packet.
Checksums
- A checksum is a piece of data which is generated from the payload.
- When data is assembled into packets, we calculate the checksum and send this along with the packet.
- When the data is received, the recipient can re-calculate the checksum from the data they receive and compare it to the checksum they received.
- If the values are different, then some of the data was corrupted.
- They can then request the data again.
Confirmation message
- If all packets have been successfully received, then a confirmation message is sent to the sender.
- This lets them know that there were no issues in transmission that they might need to fix.
Test yourself on Did my Data Arrive Safely?
Why might data not arrive as intended?
What is a timeout limit?
Error-Checking Data Using Checksum