IPoIB-RC and Checksums

In GbE usually the NIC Tx Segmentation (large send) capability comes
hand in hand with Checksum offload for greater efficiency (and zero
copy)

On UD we decided not to address checksum offloading, since we cannot
guarantee that the node will not forward an un-checked packet 

Where as in RC we can have examples of devices that can guarantee
checksum 
One example is an IB-IP gateway that always checksum outgoing and
incoming packets, and can act as a remote IP NIC to the Host  

I suggest we include a checksum option in the CM Exchange 
Where a node can request that its peer will not checksum the packet for
it
And also signal that he sends packets that are already checked 
That can help improve performance of IPoIB RC

P.S. another note, we discussed in IETF was that we may want to
mention/suggest (not mandate) use of SRQ for IPoIB-RC in order to
preserve memory 

Yaron