Meta is betting AI on the network: Ethernet scale-up via ESUN, 102.4T liquid-cooled switches with a two-tier fabric, and SRv6 on FBOSS across buildings. Open specs make it easier for white-box ODMs to get in, and harder to stay differentiated.

At the same 500 m, pluggables draw 23 pJ/bit while OCI needs 7, a gap of about 230 W per XPU. Broadcom says Ethernet scale-up is in production, copper gets one more in-rack generation with 400G PAM6, and optics must match copper power to enter.

Meta's Tahan is an Ethernet scale-up switch built by subtraction: same FBOSS, routing and multipath off. The switch holds about 98.5% of the latency budget, and next gen grows links 13.5x while per-accelerator bandwidth grows only 1.5x.