Recommended data size to avoid fragmentation over UDP?

Question

I am designing a UDP-based system and need to know the recommended maximum data packet size. The typical MTU for Ethernet v2 is, as I understand it, 1500 bytes. However, if PPoE is used, that drops to 1492.

Does that mean that the data portion of my system should be 1492 bytes maximum to avoid fragmentation on typical networks or should I just ignore PPoE and make it 1500 bytes??

Answer 1

Per RFCs 1122-3, IP routers are required not to fragment packets of 576 octets or less. Subtracting the 8 byte UDP header and the 20 byte IP header, this leaves you 548 bytes of payload. However the figure usually cited for UDP non-fragmentation is 534 bytes.