I am trying fragmentation with IPV6.Using scapy to craft packets. My payload size is 1400 bytes and fragment size chosen is 500 bytes and sending 3 fragments such that last fragment is never sent. I am seeing that scapy is generating fragment with payload size 432 bytes. Fragment extension header is around 8 bytes. IPV6 header is 40 bytes.
If we sum it all then frag size is coming upto 480 bytes,whereas i have specified it to be 500 bytes. How is this calculation done? and how was the frag payload size decided to be 432 bytes?