{
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-11-02",
  "slug": "priority-flow-control",
  "term": "Priority-based Flow Control (PFC)",
  "aliases": [
    "PFC",
    "Priority Flow Control"
  ],
  "definition": "Priority-based Flow Control pauses selected Ethernet traffic priorities on a link to avoid frame loss caused by congestion.",
  "note": "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. [pfc-standard]\n\nPause 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. [pfc-operation]\n\nZhu 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. [dcqcn15]",
  "related": [
    "data-center-bridging",
    "fcoe"
  ],
  "citations": [
    {
      "id": "pfc-standard",
      "title": "IEEE 802.1Qbb: Priority-based Flow Control, project scope",
      "url": "https://1.ieee802.org/dcb/802-1qbb/",
      "accessed": "2026-11-02"
    },
    {
      "id": "pfc-operation",
      "title": "Cisco Nexus 9000 NX-OS QoS Guide, Release 10.5(x): Configuring Priority Flow Control",
      "url": "https://www.cisco.com/c/en/us/td/docs/dcn/nx-os/nexus9000/105x/configuration/qos/cisco-nexus-9000-series-nx-os-quality-of-service-configuration-guide-105x/m-configuring-priority-flow-control.html",
      "accessed": "2026-11-02"
    },
    {
      "id": "dcqcn15",
      "title": "Zhu et al., Congestion Control for Large-Scale RDMA Deployments, SIGCOMM 2015, section 2.2 and Figures 2-4. DOI 10.1145/2785956.2787484.",
      "url": "https://conferences.sigcomm.org/sigcomm/2015/pdf/papers/p523.pdf",
      "accessed": "2026-11-02"
    }
  ],
  "provenance": [
    "Specification scope, vendor documentation and a historical RoCEv2 experiment are distinct evidence types; no hardware test was performed by Hesela."
  ]
}