RoCEv2

RoCEv2 carries RDMA traffic inside UDP/IP packets (UDP destination port 4791), so it is routable across standard Layer-3 Ethernet. RDMA lets one host read or write another host’s memory directly, bypassing the CPU and kernel for very low latency and high throughput. Because RDMA is sensitive to loss, RoCEv2 fabrics rely on congestion and flow control such as ECN and PFC to stay near-lossless. It is widely used for GPU and storage interconnects in AI/HPC clusters.