ConnectX
NVIDIA's network adapter line, carrying the RDMA, hardware timestamping, and reordering features a fabric's transport depends on; its firmware is a first-class item in cluster version lockstep.
Current numbers
2x400GbEConnectX-8: the single 800 Gb/s physical port runs Ethernet as 2×400GbE (single 800GbE link unsupported; XDR IB carries 800G on the same port) — the dual-plane substrate
up to 1.6 Tb/sper-GPU scale-out bandwidth on the Rubin platform — two 800 Gb/s ConnectX-9 SuperNICs per GPU, not one 1.6T NIC; double the ConnectX-8 generation; BlueField-4 (integrates a CX-9) at 800 Gb/s
< 4 nsinternal ASIC sync error (Spectrum) and ConnectX-class NIC timestamp variance