The Ultra Ethernet Transport specs aren't public yet so I can only quote the public whitepaper [0]:
"The UEC transport protocol advances beyond the status quo by providing the following:
● An open protocol specification designed from the start to run over IP and Ethernet
● Multipath, packet-spraying delivery that fully utilizes the AI network without causing congestion or head-of-line blocking, eliminating the need for centralized load-balancing algorithms and route controllers
● Incast management mechanisms that control fan-in on the final link to the destination host with minimal drop
● Efficient rate control algorithms that allow the transport to quickly ramp to wire-rate while not causing performance loss for competing flows
● APIs for out-of-order packet delivery with optional in-order completion of messages, maximizing concurrency in the network and application, and minimizing message latency
● Scale for networks of the future, with support for 1,000,000 endpoints
● Performance and optimal network utilization without requiring congestion algorithm parameter tuning specific to the network and workloads
● Designed to achieve wire-rate performance on commodity hardware at 800G, 1.6T and faster Ethernet networks of the future"
You can think of it as the love-child of NDP [2] (including support for packet trimming in Ethernet switches [1]) and something similar to Swift [3] (also see [1]).
I don't know if UET itself will be what wins, but my point is the industry is taking the problems seriously and innovating pretty rapidly right now.
Disclaimer: in a previous life I was the editor of the UEC Congestion Control spec.
[0] https://ultraethernet.org/wp-content/uploads/sites/20/2023/1...
[1] https://ultraethernet.org/ultra-ethernet-specification-updat...
[2] https://ccronline.sigcomm.org/wp-content/uploads/2019/10/acm...
[3] https://research.google/pubs/swift-delay-is-simple-and-effec...