From http://Connect.Microsoft.Com:

You may have noticed the much improved performance of HPC Server 2008 MS-MPI on multi-core compute nodes due to the all-new implementation of shared memory communications (between processes on a single node).  But did you know that MS-MPI also has a brand new RDMA networking interface called NetworkDirect which pipes the blazing performance of today’s RDMA networking fabrics directly into MS-MPI?  You can try it now with your existing Infiniband networking gear and experience for yourself the performance boost the MS HPC team sees in our 256-node, 2048-processor scale testing cluster-  30% improvement in our Top500 run with no changes to our existing cluster hardware!  And it’s stable as a rock.  You really owe it to yourself to try this if you’ve got Infiniband gear on your cluster. 

You can download NetworkDirect drivers that work with all Mellanox-based Infiniband hardware (from Mellanox, Cisco, Voltaire) here:

https://docs.mellanox.com/dm/WinIB/ReadMe.html    (Note:  This provider does not yet support the new ConnectX hardware)

NetworkDirect Providers available soon for other RDMA fabrics such as iWARP and Myrinet.