A municipal AI factory sees PFC storms after enabling lossless RoCE on Spectrum-X. Engineers want congestion signaled without endless pause frames. Which action fits?
Select an answer to reveal the explanation.
Short Explanation
PFC storms are like every traffic light stuck on red forever—nothing moves. ECN is the early yellow: Spectrum-X marks congestion so senders slow down before pause frames take over the municipal AI fabric. Turn ECN on and verify it with PFC, you'll want to avoid tuning RED drop thresholds on the lossless queue to drop packets early under sustained congestion, raising PFC trigger thresholds to allow deeper buffering before pause frames are generated, and mapping RoCE traffic to a best-effort priority with ECN marking for end-to-end rate reduction.
Full Explanation
When a municipal AI factory sees PFC storms after enabling lossless RoCE on Spectrum-X, engineers should enable and verify ECN alongside PFC so congestion is marked before pause frames dominate. Explicit Congestion Notification lets senders slow down earlier, reducing reliance on Priority Flow Control pause storms that freeze queues and spread head-of-line blocking. PFC remains part of the lossless toolkit, but ECN provides the proactive signal Spectrum-X AI fabrics need under load.
Tuning RED drop thresholds on the lossless queue to drop packets early under sustained congestion is wrong because it drops packets prematurely, starving the lossless RoCE class and breaking the AI factory's lossless guarantees. Raising PFC trigger thresholds to allow deeper buffering before pause frames are generated is wrong because it delays pause frames until buffers overflow, causing burst loss and worsening head-of-line blocking in the municipal AI fabric. Raising PFC trigger thresholds to allow deeper buffering before pause frames are generated similarly drops the proactive congestion control municipal AI collectives expect. Mapping RoCE traffic to a best-effort priority with ECN marking for end-to-end rate reduction is wrong because it strips lossless guarantees from RoCE, turning the AI factory's critical traffic into best-effort and failing to provide the lossless service Spectrum-X requires.
Exam caveat: PFC storms point to missing or unverified ECN/QoS balance—not to merely raising PFC trigger thresholds to allow deeper buffering before pause frames are generated. Operational check: enable ECN with PFC on the Spectrum-X RoCE class, generate congestion, confirm ECN-marked packets and reduced pause rates in telemetry, and tune RED drop thresholds on the lossless queue so municipal training recovers without endless PFC storms. In practice, tune RED drop thresholds on the lossless queue so marks appear under synthetic congestion before PFC counters spike across the municipal AI factory; if pause storms persist, revisit buffer and QoS maps rather than raising PFC trigger thresholds to allow deeper buffering on Spectrum-X.