Which for some reason is not in the abnf spec, and thus will be ignored up until somebody tries to implement this and fails a compatibility test.<p>Please put it in your abnf spec. People use them, you know.<p>Yes, it&#x27;s hard to specify. The problem is that you have both an uncapped ID and an uncapped PAYLOAD in the same message. I recommend giving ID a max length of, say, 32, and PAYLOAD then has a max length of 951 if I&#x27;m counting right.<p>Or you could consider that an IPv6 path MTU is at least 1280, and use that (or 1232) as your per message bound instead of 1024. You&#x27;re sending a packet, might as well get full value.