Richard Frank wrote:
Hmmm - so what happens with IWARP NIC when no buffer is posted on recv q and a message arrives ?
The spec sez the implementation can terminate the connection. That is exactly what ammasso and chelsio's rnics do. The spec doesn't mandate this behavior however. So an incoming SEND could to be dropped and not ack'd at the TCP level forcing the client to retransmit. But I don't know of an rnic that does this.
FYI: The reason the rnic implementation might terminate in this case is due to the protocol stack layering. If the rdma layers (mpa, ddp, rdmap) sitting on top of TCP don't tell TCP when to ack something, then the incoming SEND might be acked by TCP before the RDMA layers process the packet. Then the SEND cannot be dropped since its already acked. So the message either must be buffered until the RECV is posted, or the connection terminated.
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