USFP vs OSFP

OSFP is the module most 800G and 1.6T AI networks run on today. USFP is the same size, give or take, but carries four times the bandwidth, so the obvious question is whether it replaces OSFP. In the long run that's the plan for the fastest ports. In the short run the two won't share a cage.

Side by side

OSFP and OSFP-XD from the OSFP MSA white paper; USFP from Cisco and NVIDIA.

Where the 4x comes from

Twice the lane rate times twice the lanes. An OSFP1600 module runs eight lanes of 200G; USFP runs sixteen of 400G. Because the module is about the same size, the bandwidth through each front-panel opening goes up four times, from 1.6T to 6.4T. OSFP-XD got to 16 lanes first, but at 200G per lane and in a taller module that only reaches 3.2T.

Heat

The OSFP MSA rates its integrated heatsink at more than 30 W, and OSFP-XD at up to 40 W for 1.6T-ZR and 3.2T modules. USFP's ceiling is 100 W, still without a cooling circuit inside the module. Analysts expect a switch full of 100 W modules to push many designs toward liquid-cooled chassis anyway (NAND Research).

Will my OSFP switches take USFP?

Plan on no. USFP uses a different connector, a two-dimensional contact array instead of OSFP's card edge, so it needs new cages, which means new switches and network cards. Neither Cisco nor NVIDIA claims compatibility with OSFP ports. OSFP-XD set the precedent: its cages are keyed so an OSFP module can't be pushed in by mistake.

That's less of a problem than it sounds. A 400G-per-lane switch chip will be a new switch regardless, and its 1.6T ports could be served by either format. The open question is which cage that switch ships with.

Which to plan for

For anything you buy in the next year or two, OSFP: it's what 200G-per-lane switches use, and the supply chain is mature. USFP is a planning input for the 400G-per-lane generation, when switches with those chips are announced. Our tracker will show when that happens.

• USFP vs XPO

  Air-friendly 6.4T against a liquid-cooled 12.8T. Two camps, two bets on the next switch chip.

• USFP vs co-packaged optics

  Keep swappable modules, or put the optics in the switch package for the lowest power.

• Every form factor

  OSFP to co-packaged optics in one table: lanes, capacity, heat and who backs each.