It is definitely possible to go much lower than 80usec on Ethernet. But obviously it depends on the scale, utilisation etc.
At the sizes of GPU clusters we're talking about these days - 32K and up - things get tricky.
The main alternative to Infiniband used in the industry is RoCE - Meta has written a lot about it [0].
There's several reasons to avoid Infiniband, such as cost, availability, vendor lock in, lack of experience etc.
Those are some of the reasons why many players are trying hard to make Ethernet work, see Ultra Ethernet [1].
[0] https://engineering.fb.com/2024/08/05/data-center-engineerin...
IIRC, Arista started off focusing on the financial market with low latency.
There's fairly well regarded in a general sense nowadays (at least /r/networking often has folks recommending them as a vendor).
Are there other technologies they could have used?
Also, the 80us is supposed to be the worst case, where typical is supposed to be <10us. Again not knowing anything about infiniband, what’s the typical perf? I tried to google but the people who are talking about it are in the know in ways I’m not.
Thanks!