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: one 800 Gb/s port runs Ethernet as 2×400GbE (single 800GbE unsupported) and XDR IB at 800G; the dual-plane substrate
~18× GB200 / ~9× GB300NVLink 5 per-GPU scale-up (~900 GB/s per direction) vs one scale-out NIC per GPU: ~18× GB200/ConnectX-7/400G, ~9× GB300/ConnectX-8/800G
up to 1.6 Tb/sRubin per-GPU scale-out bandwidth: two 800 Gb/s ConnectX-9 SuperNICs per GPU, not one 1.6T NIC; double the ConnectX-8 generation