CoRD: Converged RDMA Dataplane

HPC networking is often characterized by kernel bypass, which is considered mandatory for large parallel and distributed applications. However, kernel bypass comes at a price because it breaks the traditional OS architecture, requiring applications to use special APIs and limiting the OS's control over existing network connections. We make the case that kernel bypass is not mandatory. Rather, high-performance networking relies on multiple performance-improving techniques, with kernel bypass even being detrimental to performance under specific conditions. CoRD removes kernel bypass from RDMA networks, primarily to enable efficient OS-level control over the RDMA dataplane. This control can be used to enhance security or resource allocation policies, and, as we demonstrate in one of the use cases, can improve end-to-end application performance by up to 10%. This architecture can enable Cloud-based distributed RDMA applications and facilitate deployment of coupled HPC applications.