Dell EMC SmartFabric OS10 User Guide Release 10.5.0

• PFC is supported for 802.1p, dot1p priority traffic, from 0 to 7. FCoE traffic traditionally uses dot1p priority 3 — iSCSI storage traffic uses dot1p priority 4.
• Configure PFC for ingress traffic by using network-qos class and policy maps. For more information, see Quality of service. PFC-enabled traffic queues are treated as lossless queues. Configure the same network-qos policy map on all PFC-enabled ports. Configure required bandwidth for lossless traffic using ETS queuing (output) policies on egress interfaces.
• In a network-qos policy-class map, use commands to generate PFC pause frames for matching class-map priorities:
  • Send pause frames for matching class-map traffic during congestion using the pause command.
  • (Optional) Enter user-defined values for the reserved ingress buffer-size of PFC class-map traffic, and the thresholds that are used to send XOFF and XON pause frames using the pause [buffer-size kilobytes pause-threshold kilobytes resume-threshold kilobytes]command.
  • Configure the matching dot1p values used to send pause frames using the pfc-cos command.
  • (Optional) Set the static and dynamic thresholds that determine the shared buffers available for PFC class-map traffic queues using the queue-limit thresh-mode command.
• By default, the lossy ingress buffer handles all ingress traffic. When you enable PFC, dot1p ingress traffic competes for shared buffers in the lossless pool instead of the shared lossy pool. The number of lossless queues that are supported on an interface depends on the amount of available free memory in the lossy pool.
• Use the priority-flow-control mode on command to enable PFC for FCoE and iSCSI traffic; for example, priority 3 and 4.
• Enable DCBX on interfaces to detect and autoconfigure PFC/ETS parameters from peers.
• PFC and 802.3x LLFC are disabled by default on an interface. You cannot enable PFC and LLFC simultaneously. LLFC ensures lossy traffic in best-effort transmission. Enable PFC to enable guarantee lossless FCoE and iSCSI traffic. PFC manages buffer congestion by pausing specified ingress dot1p traffic; LLFC pauses all data transmission on an interface. To enable LLFC, use the flowcontrol [receive | transmit] [on | off] command.
• SYSTEM-QOS mode applies a service policy globally on all interfaces:
  • Create and apply a 1-to-1 802.1p-priority-to-traffic-class mapping on an interface or all interfaces in INTERFACE or SYSTEM-QOS mode.
  • Create and apply a 1-to-1 traffic-class-to-queue mapping on an interface or all interfaces in INTERFACE or SYSTEM-QOS mode.

 Dot1p Priority : 0  1  2  3  4  5  6  7
  Traffic Class : 1  0  2  3  4  5  6  7

• Apply the default trust map specifying that dot1p values are trusted in SYSTEM-QOS or INTERFACE mode.

  trust-map dot1p default
  

1. Configure a trust map of dot1p traffic classes in CONFIGURATION mode. A trust map does not modify ingress dot1p values in output flows.

   Assign a qos-group to trusted dot1p values in TRUST mode using 1-to-1 mappings. Dot1p priorities are 0 to 7. For a PFC traffic class, map only one dot1p value to a qos-group number; for Broadcom-based NPU platforms, the qos-group number and the dot1p value must be the same. A qos-group number is used only internally to classify ingress traffic classes.

   trust dot1p-map dot1p-map-name 
      qos-group {0-7} dot1p {0-7}
      exit

2. Apply the trust dot1p-map policy to ingress traffic in SYSTEM-QOS or INTERFACE mode.

   trust-map dot1p trust-policy—map-name

 Traffic Class : 0  1  2  3  4  5  6  7
         Queue : 0  1  2  3  4  5  6  7

1. Create a traffic-class-to-queue map in CONFIGURATION mode. Assign a traffic class (qos-group) to a queue in QOS-MAP mode using 1-to-1 mappings. For a PFC traffic class, map only one qos-group value to a queue number. A qos-group number is used only internally to classify ingress traffic.

   qos—map traffic-class tc-queue-map-name
      queue {0-7} qos-group {0-7}
      exit 

2. Apply the traffic-class-queue map in SYSTEM-QOS or INTERFACE mode.

   qos-map traffic-class tc-queue-map-name