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Configuring PFC
Enabling PFC
If the CE8850-64CQ-EI is used as the aggregation switch, the recommended configurations are the same as those for access switches in Enabling PFC.
If the CloudEngine 16800 is used as the aggregation switch, the configuration method is as follows:
# Configure the queue with priority 4 to carry RoCEv2 traffic on the network. To implement this, enable PFC for priority 4 on each interface and implement PFC based on the priority mapped from the DSCP value.
<HUAWEI> system-view [~HUAWEI] dcb pfc //Enter the view of the default PFC profile. [*HUAWEI-dcb-pfc-default] priority 4 //Enable PFC for priority 4. [*HUAWEI-dcb-pfc-default] quit [*HUAWEI] interface 100ge 1/0/1 [*HUAWEI-100GE1/0/1] dcb pfc enable mode manual //Configure PFC to work in forcible mode. [*HUAWEI-100GE1/0/1] quit [*HUAWEI] dcb pfc dscp-mapping enable slot 1 //Implement PFC based on the priority mapped from the DSCP value. [*HUAWEI] commit
Precautions:
- If you configure both priority mapping and PFC, exercise caution when modifying the mappings between the priorities of PFC-enabled queues and priorities in the DiffServ domain. Otherwise, PFC may not work.
In the following scenarios, if a queue is congested, PFC may fail to be triggered and does not take effect:
The configured threshold for triggering PFC frames is too high.
The configured queue buffer threshold is too low.
Verifying the PFC configuration
After PFC is configured successfully, the default PFC threshold is automatically allocated to lossless queues. The default thresholds vary according to the version and device. For details about how to manually configure the PFC thresholds, refer to Adjusting the Buffer and PFC Thresholds.
<HUAWEI> display dcb pfc buffer Xon: PFC backpressure stop threshold Xoff: PFC backpressure threshold Hdrm: Headroom buffer threshold Guaranteed: PFC guaranteed buffer threshold The actual PFC backpressure stop threshold is the higher value between the value of xon and the difference between the value of xoff and the value of xon-offset. C:cells B:bytes K:kilobytes M:megabytes D:dynamic alpha ------------------------------------------------------------------------------------ Interface Queue Guaranteed Xon Xon-Offset Xoff Hdrm ------------------------------------------------------------------------------------ 100GE1/0/1 4 10(C) 50(C) 20(C) 85(C) 168(C) -----------------------------------------------------------------------------------