Consistently Losing Fragments with Large Packets
 

I've got a Windows application communicating with a Linux application and am having problems receiving UDP packets larger than about 9000 bytes in the Linux application.

I'm running wireshark and seeing how the packet is fragmented in Windows and am running tcpdump in Linux and seeing that once I get a packet with more than 5 fragments I lose the last couple of fragments. Packets with 5 or fewer fragments are always received.

I understand that losing packets is part of UDP, but I shouldn't always be losing the same packets once I get to a certain size of message.

I'm led to believe I have some sort of packet buffer size problem but can't figure it out.

I've set /proc/sys/net/rmem_max to something like 64k but no luck.

Any ideas?

Set the IP MTU to 1450 bytes so that the packets don't need to be fragmented. (1450 leaves some room for ethernet, pppoe, and vpn headers.)