> 1) There is a field MTU in the IP header. You don't need this in every packet, you only need it in one packet (or once every few minutes). Instead of putting

> 1) There is a field MTU in the IP header. You don't need this in every packet, you only need it in one packet (or once every few minutes). Instead of putting a field in every packet that only <1% of them need, we could create an out of band message to notify when the MTU has been exceeded. And the endpoint that needs to know that is the sender, so that's who you would send it to. Which is what they did. That works perfectly well, the problem is that many misconfigured firewalls drop the ICMP messages. No one predicted that level of incompetence when the protocols were being designed.