Install Guide

NOTE: The detail option display the current headroom pool usage in each of the Pipelines in the device.
DellEMC#show hardware buffer headroom-pool buffer-info
------Buffer Details for Stack-Unit 1 portpipe 0 ------
-----------------------------------------------------------------
Headroom-Pool Configured Buffer(KB) Used Buffer(KB)
-----------------------------------------------------------------
HP1 0 0
DellEMC#
Monitoring Buffer Statistics for Tracking Purposes
Using the buffer statistics tracking feature, you can monitor the peak buffer usage of the head room pool over a specific period
of time. This monitoring enables you to optimize the head room pool size based on real-time network traffic data.
To view the peak head room pool usage details during a specific monitoring period:
Enter the following show command:
EXEC Privilege Mode
show hardware buffer-stats-snapshot resource headroom-pool [detail]
NOTE: The detail option display the peak headroom pool usage in each of the Pipelines in the device.
DellEMC#show hardware buffer-stats-snapshot resource headroom-pool
---------------------------------------
HP# PEAK USE COUNT(CELLS)
---------------------------------------
0 0
1 0
2 0
3 0
DellEMC#
Behavior of Tagged Packets
The below is example for enabling PFC for priority 2 for tagged packets. Priority (Packet Dot1p) 2 will be mapped to PG6 on
PRIO2PG setting. All other Priorities for which PFC is not enabled are mapped to default PG – PG7.
Classification rules on ingress (Ingress FP CAM region) matches incoming packet-dot1p and assigns an internal priority (to
select queue as per Table 1 and Table 2).
The internal Priority assigned for the packet by Ingress FP is used by the memory management unit (MMU) to assign the packet
to right queue by indexing the internal-priority to queue map table (TABLE 1) in hardware.
PRIO2COS setting for honoring the PFC protocol packets from the Peer switches is as per above Packet-Dot1p->queue table
(Table 2).
The packets come in with packet-dot1p 2 alone are assign to PG6 on ingress.
The packets come in with packet-dot1p 2 alone use Q1Q2 (as per dot1p to Queue classification – Table 2) on the egress port.
● When Peer sends a PFC message for Priority 2, based on above PRIO2COS table (TABLE 2), Queue 1Queue 2 is halted.
● Queue 1Queue 2 starts buffering the packets with Dot1p 2. This causes PG6 buffer counter to increase on the ingress, since
P-dot1p 2 is mapped to PG6.
● As the PG6 watermark threshold is reached, PFC generates for dot1p 2.
Configuration Example for DSCP and PFC Priorities
Consider a scenario in which the following DSCP and PFC priorities are necessary:
DSCP
0 – 5, 10 - 15 20 – 25, 30 – 35
Data Center Bridging (DCB) 259