We have been looking on SDP performance, when connecting Open Fabrics OFED (InfiniBand software stack for Linux) when connecting to old Proprietary software stacks. What we have discovered is that OFED is using protocol major version 2 and the proprietary solutions uses major version 1. This can cause a reduction is the available bandwidth between the 2 hosts.
The way to solve it is to force OFED driver to use major version 1 or to get the proprietary providers change their code to use version 2.