Remote Direct Memory Access (RDMA) is a high-performance networking technology that allows direct message passing from application virtual memory on one system to application virtual memory on another system. This message passing not only avoids the intermediate buffer copies that are required by TCP, but also bypasses the operating system kernel, resulting in higher throughput, lower latency, and lower CPU utilization than can be obtained on traditional networks. The three popular transport implementations of RDMA are InfiniBand, iWARP (Internet Wide-Area RDMA Protocol), and RoCE (RDMA over Converged Ethernet). The software layer is provided by the OpenFabrics Software (OFS) verbs library, which provides direct access to the RDMA hardware from userspace. The verbs library is powerful but also daunting to the network programmer, due to the complexity of direct access to the hardware.
