What guarantees does UDP provide?

UDP provides a minimum of guarantees. This is done deliberately, to ensure simplicity and minimal latency.

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#What guarantees UDP does have

#1. Message boundaries are preserved

UDP transfers data as messages (datagrams):

• one send = one message
• if a message arrives, it arrives whole

This means:

• UDP does not merge and does not split messages for the application

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#2. "Best effort" delivery

UDP tries to deliver data:

• without promises
• without retries
• without acknowledgments

If a message arrives, the application will receive it. If not, UDP does nothing about it.

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#What UDP does NOT guarantee (important)

UDP does not guarantee:

• data delivery
• delivery order
• the absence of duplicates
• the integrity of the data stream
• speed control
• congestion control
• connection establishment

All of these tasks, when needed, must be solved by the application itself.

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#Comparing TCP and UDP guarantees

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#Why UDP is still used

Because sometimes what matters more is:

• minimal latency
• predictable delivery time

than perfect reliability.

That is why UDP is used for:

• VoIP
• video streaming
• online games
• DNS

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#In short, for the interview

UDP does not guarantee the delivery, order, or integrity of data transmission; it only provides delivery of individual messages without establishing a connection and with minimal overhead.