For RoCEv2 public-safety trainers, how should Priority Flow Control and Explicit Congestion Notification be positioned relative to each other on the municipal fabric?

For RoCEv2 public-safety trainers on the municipal fabric, Priority Flow Control and Explicit Congestion Notification should be enabled together as complementary tools: PFC provides lossless pause on the AI priority, while ECN provides early congestion signaling so endpoints can slow before pause storms dominate. Enabling PFC and ECN together as sequenced controls with lossless pause first and delayed ECN marking breaks the complementary design by letting pause fire before endpoints receive early slow-down signals. Using delayed ECN marking on the AI priority forces the fabric to depend on pause first, inviting pause storms and losing the early CE marks that let endpoints throttle senders in time. Enabling PFC and ECN together as complementary controls for default storage traffic misplaces both tools away from the AI training class that needs them. Enabling PFC and ECN together with global standard pause plus early ECN marking for RoCEv2 AI traffic replaces priority-based PFC with generic pause, halting all priorities instead of pausing only the AI class and leaving public-safety collectives exposed to head-of-line blocking. Exam caveat: complementary use still requires coherent Cos maps and endpoint support for ECN reaction; enabling both with mismatched priorities can still fail. Operational check: enable PFC and ECN on the RoCEv2 public-safety AI priorities, run an incast-style load test, confirm CE marks appear early and pause activates only as needed, and verify trainers complete without disabling either control.