I guess I knew this, but I’m used to thinking about problems like this at the application layer rather than down in protocol:
“These problems exist in TCP, the poster child for Postel’s principle. It is possible to make different machines see different input, by building packets that one machine accepts and the other rejects.”
This is a good article.
http://programmingisterrible.com/post/42215715657/postels-principle-is-a-bad-idea