This networking enhancement is new in the Developer 5/07 release.
The Sockets Direct Protocol (SDP) is a transport protocol layered over the Infiniband Transport Framework (IBTF). SDP is a standard implementation based on Annex 4 of the Infiniband Architecture Specification Vol1. SDP provides reliable byte-stream, flow controlled, two-way data transmission which is very similar to TCP.
For more information, see the sdp(7D) man page.