A server vendor builds an eight-GPU training node where every GPU must reach every other GPU at full point-to-point NVLink bandwidth simultaneously, not just its directly cabled neighbours. Direct GPU-to-GPU NVLink wiring alone cannot give all pairs full bandwidth at once. Which component provides the non-blocking all-to-all switching needed inside the node?
- AA PCIe Gen5 switch that fans the GPUs out to the host root complex and arbitrates their peer-to-peer transfers
- BA BlueField DPU that terminates the NVLink fabric and forwards GPU memory transactions through its embedded Arm cores
- CAn InfiniBand HDR switch placed inside the chassis to carry the GPU-to-GPU collective traffic between the eight GPUs
- DAn NVSwitch fabric that cross-connects every GPU's NVLink ports so any pair communicates at full NVLink bandwidth concurrently Correct
Why A is wrong: Tempting because a PCIe switch does interconnect devices, but PCIe peer-to-peer is far slower than NVLink and routing GPU traffic through the host complex is exactly the bottleneck NVLink exists to bypass.
Why B is wrong: The DPU is genuine hardware, but it offloads networking, storage, and security at the host boundary; it does not switch intra-node NVLink traffic, so it cannot deliver all-to-all GPU bandwidth.
Why C is wrong: InfiniBand is the scale-out fabric between nodes, not an intra-node memory interconnect; routing eight on-board GPUs through an InfiniBand switch would add NIC and protocol latency that NVSwitch avoids entirely.
Why D is correct: Correct: NVSwitch is the on-board crossbar that interconnects all GPUs' NVLink lanes, giving non-blocking all-to-all connectivity so every GPU pair exchanges data at full NVLink bandwidth at the same time.