> On other hand, if UDP checksum is omitted and under certain
> conditions (long UDP datagram timeout, high communcation speed and as
> a result IP overlapping while still within a UDP datagram timeout) -
> one might expect to get a wrong, but "valid" datagram with IP
> fragment belonging to another UDP datagram. - I think, it might
> happen with IPv4.
Attributing fragments of one datagram to a different datagram
would definitely be a bug in the network stack.
That's the purpose of the Identification field.
(and Fragment Offset to a lesser degree.)