Why do Lossy RoCE Accelerations change RDMA Write {First, Middle, Last} to RDMA Write Only?


I have a 100G Mellanox RDMA NIC (MT27800 Family [ConnectX-5]) installed for RoCE and setup lossy RoCE Accelerations according to https://community.mellanox.com/s/article/How-to-Enable-Disable-Lossy-RoCE-Accelerations.

However after enabling these feature RDMA Writes larger than the MTU which have previously been fragmented into RDMA Write {First, Middle, Last} are only sent as multiple RDMA Write Only.

Is this intended behaviour? (see attached packet dump)

Another thing I observed is that now If sending multiple packets, a few RDMA Write packets have the request-ACK bit set even though they are not the last packet of a fragmented write. This was not the case without Lossy RoCE Accel. enabled.

Best regards,


Hi Matthias

It is expected behavior which for better performance