InfiniBand is a purpose-built network interconnect designed for high bandwidth and low, predictable latency between compute, storage, and accelerator nodes. Unlike TCP/IP stacks, it integrates RDMA natively, allowing applications to exchange messages directly into memory without CPU or kernel involvement via queue pairs and a verbs-based programming model. The fabric enforces lossless behavior through credit-based flow control, avoiding retransmissions and tail-latency spikes common in Ethernet environments. Key use cases include distributed AI training, HPC simulations, NVMe over Fabrics, and GPU Direct RDMA. Operational challenges include fat-tree topology design and cabling symmetry, Subnet Manager placement and failover, software stack alignment (OFED, kernel drivers, HCA firmware), avoiding unintended IPoIB fallback, and continuous validation using tools like ibdiagnet and perftest benchmarks.
