Remote Direct Memory Access (RDMA) is a high-performance networking technology that enables zero-copy data transfers directly between application memory spaces across networked systems. By bypassing the operating system (OS) networking stack, RDMA eliminates CPU overhead and context switches, significantly reducing latency and improving throughput.


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RDMA Architecture & Mechanism

RDMA operates through specialized network interface cards (RNICs) that handle transport protocol processing and direct memory operations in hardware. Key features include:

  • Zero-Copy Data Transfers: Applications can read/write remote memory without CPU intervention.
  • Bypassing Kernel Overhead: Eliminates traditional network stack processing, reducing latency to sub-microsecond levels.
  • Explicit Memory Registration: Memory regions must be registered with the RNIC, which maintains virtual-to-physical address translation for secure access.

RDMA supports two transport modes:

  • Reliable Connected (RC): Guarantees in-order, reliable delivery for critical workloads.
  • Unreliable Datagram (UD): Optimized for low-latency applications where minor packet loss is acceptable.

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InfiniBand: High-Performance RDMA Networking

InfiniBand is a widely adopted RDMA-based networking architecture designed for high-performance computing (HPC) and data-intensive applications. It provides:

  • Ultra-Low Latency: Achieves as low as 600 nanoseconds end-to-end.
  • High Bandwidth: Supports data rates from 10 Gb/s (SDR) to 100 Gb/s per port over copper or optical fiber.
  • Host Channel Adapters (HCAs): Offload protocol processing and memory translation to hardware, reducing CPU load.

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RDMA & InfiniBand in Modern Computing

These technologies are critical for:

  • Distributed Machine Learning: Efficient communication for large-scale AI training workloads.
  • HPC & Scientific Computing: Accelerated data sharing across compute clusters.
  • Cloud Data Centers: Optimized storage access (NVMe-over-Fabrics) and disaggregated computing.

With hardware acceleration and direct memory access, RDMA and InfiniBand deliver unparalleled speed, efficiency, and scalability in next-generation computing environments.

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