hesela.devPriority-based Flow Control (PFC)
Priority-based Flow Control pauses selected Ethernet traffic priorities on a link to avoid frame loss caused by congestion.
PFC operates on priorities on a full-duplex link, not on individual application flows. Avoiding congestion drops is not a guarantee of data integrity, write persistence or recovery. [1]
Pause propagation can stall a traffic class across multiple links. The cited switch guide documents a watchdog that drops traffic when a no-drop queue remains stuck; this is release-specific behavior, not a requirement for all PFC implementations. [2]
Zhu et al.'s SIGCOMM 2015 RoCEv2 experiments show that a victim flow can be slowed by congestion outside its path because pause messages cascade. Their testbed result is not an FCoE measurement or a universal throughput estimate. [3]
Relations
- related
- Data Center Bridging (DCB), FCoE
Citations
- IEEE 802.1Qbb: Priority-based Flow Control, project scope
- Cisco Nexus 9000 NX-OS QoS Guide, Release 10.5(x): Configuring Priority Flow Control
- Zhu et al., Congestion Control for Large-Scale RDMA Deployments, SIGCOMM 2015, section 2.2 and Figures 2-4. DOI 10.1145/2785956.2787484.
Sources & caveats
- Specification scope, vendor documentation and a historical RoCEv2 experiment are distinct evidence types; no hardware test was performed by Hesela.