RoCE (RDMA over Converged Ethernet)
Beginner
A way to run RDMA, the fast copy-straight-into-memory kind of networking, over Ethernet. Ethernet is the network most datacenters use.
Novice
RDMA carried over Ethernet. Version 2 (RoCEv2) wraps the InfiniBand transport in standard IP and UDP headers, so it can be routed through normal data-center switches.
Expert
RoCEv2 puts the IB transport header and payload inside Ethernet/IP/UDP (destination port 4791). The source UDP port per queue pair gives ECMP its entropy. Classic RoCE NICs use go-back-N recovery, so deployments add PFC to make the Ethernet fabric lossless.
Explained in Scale-out networking (Systems).
See also: RDMA, PFC (priority flow control).