Is a UDP packet guaranteed to be complete, practical sense, if delivered?

Question

Is it a well known fact that UDP (User Datagram Protocol) is not secure, because the order of the packets sent with it may not be delivered in order, even at all. However if an UDP packet is delivered. Are the information in that packet in practical sense (99.99% and above), guaranteed to be correct?

Is a UDP packet quaranteed to be complete (not corrupted) if delivered, in practical sense (99.99% and above)?

Thanks in advance!

Answer 1

No for two reasons:

• UDP checksums are not mandatory (with IPv4). So corrupted packets can be delivered to applications.
• Internet checksums can clash much more frequently than other hashes. So even if the checksum matches, the data may be corrupted.

Answer 2

I am no expert but as far as I know, although there isn't any guarantee that the package reaches the destination at all in the most cases it should be correct if it reaches the destination. I think that should be the case because normally there is an error check (Frame Check Sum) on the Data Link Layer.