Second, while it’s certainly true that having to buffer packets to calculate the checksum is more expensive that doesn’t mean that the best option is to ignore concerns about data integrity which was a far more frequent source of problems. If they hadn’t developed an encapsulation mechanism, using an alternate protocol like UDP-Lite would avoid the issue and anyone needing extremely high-precision already has to have tight enough control over their network to deploy it since they’d need to avoid having random middleboxes interfering with timing.