ecn
AI infra interview questions tagged ecn, across every topic.
2 questions · 2 unlocked for you
Concepts behind "ecn"
The curriculum that explains the ideas these questions test.
Core
RDMA, InfiniBand and RoCEv2Training across nodes moves hundreds of gigabytes per step, and a CPU-driven TCP stack cannot feed a 400 Gb/s link. RDMA lets a NIC write straight into a remote GPU's memory with no kernel and no copies, and it runs over two fabrics: InfiniBand, which is lossless by design, and RoCEv2, which is Ethernet made lossless by configuration. The choice is operational as much as technical, and the numbers that decide it are per-GPU bandwidth, the collective's volume, and who will debug a pause storm at 3 a.m.🔌 Networking & StorageSign in
Advanced
Congestion Control for AI FabricsCollective traffic is the worst case a network can see: hundreds of senders transmit to the same receiver at the same instant (incast), every flow is large and long-lived, and RDMA cannot tolerate a dropped packet. Congestion control is the set of mechanisms (PFC, ECN with DCQCN, adaptive routing, packet spraying) that keep queues from overflowing without stalling the fabric. On plain Ethernet a busy all-reduce can fall to about 60% of link rate; with a tuned control loop it holds above 90%. Reading the counters that show which one you have is the on-call skill.🔌 Networking & Storage🔒 Premium