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Hierarchy Level

Release Information

Statement introduced in Junos OS Release 17.4R1 for the QFX Series.


Explicitly map a forwarding class to a priority-based flow control (PFC) priority value.

To support lossless behavior for untagged traffic across Layer 3 connections to Layer 2 subnetworks, you can configure PFC to be invoked based on a configured 6-bit Distributed Services code point (DSCP) value in the Layer 3 IP header, rather than an IEEE 802.1p code point in a VLAN header at Layer 2. However, because PFC sends Layer 2 pause frames specifying a PFC priority on which to notify the peer about congestion, this statement defines the PFC priority to use in pause frames when PFC is triggered by a configured DSCP value.

DSCP-based PFC is used to support Remote Direct Memory Access (RDMA) over converged Ethernet version 2 (RoCEv2).

To enable DSCP-based PFC:

  • Use this statement to map a lossless forwarding class to a PFC priority value to use in the PFC pause frames.

  • Use the [edit class-of-service congestion-notification-profile name input] dscp statement to define an input congestion notification profile to enable PFC on traffic specified by a desired DSCP value.

  • Use the [edit class-of-service classifiers] dscp statement to set up a DSCP classifier for the desired DSCP value and forwarding class mapped to a PFC priority above.


pfc-priority—3-bit PFC priority value in decimal form (0-7).

Required Privilege Level

interface—To view this statement in the configuration.

interface-control—To add this statement to the configuration.