Users Guide

Configuration notes
Dell EMC PowerSwitch S4200-ON Series:
● Provisioning PFC is not supported when deep buffer mode is enabled.
● Configure the traffic class ID to queue mapping policy on egress interfaces.
● You cannot enable PFC on all the physical interfaces, when you have split the ports to multiple breakout interfaces. For more
information, see the 'PFC configuration notes' section in the Dell EMC SmartFabric OS10 User Guide.
● When you add or remove the PFC configuration on an interface, the interface gets flapped. Stop the traffic before applying
or modifying the PFC configuration.
PFC configuration notes
● 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.
Configure dot1p priority to traffic class mapping
Decide if you want to use the default 802.1p priority-to-traffic class (qos-group) mapping or configure a new map. The
default dot1p to traffic class map in OS10 is shown below.
Dot1p Priority : 0 1 2 3 4 5 6 7
Traffic Class : 1 0 2 3 4 5 6 7
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