Users Guide

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
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HP# PEAK USE COUNT(CELLS)
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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.
Classication 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 Q2 (as per dot1p to Queue classication – Table 2) on the egress port.
• When Peer sends a PFC message for Priority 2, based on above PRIO2COS table (TABLE 2), Queue 2 is halted.
• Queue 2 starts buering the packets with Dot1p 2. This causes PG6 buer 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.
SNMP Support for PFC and Buer Statistics Tracking
Buer Statistics Tracking (BST) feature provides a mechanism to aid in Resource Monitoring and Tuning of Buer Allocation. The Max Use
Count mode provides the maximum value of the counters accumulated over a period of time.
Priority Flow Control (PFC) provides a link level ow control mechanism, which is controlled independently for each frame priority. The goal
of this mechanism is to ensure zero loss under congestion in DCB networks.
Dell EMC Networking OS provides SNMP support for monitoring PFC and BST counters, and statistics. The enhancement is made on
DELL-NETWORKING-FPSTATS-MIB with additional tables to display the PFC and BST counters and statistics.
The following tables are available in DELL-NETWORKING-FPSTATS-MIB:
• dellNetFpEgrQBuSnapshotTable
• dellNetFpIngPgBuSnapshotTable
• dellNetFpStatsPerPgTable
• dellNetPfcPerPrioTable
dellNetFpEgrQBuS
napshotTable
This table fetches the BST statistics at Egress Port for the buer used. This table displays the Snapshot of the
Buer cells used by Unicast and Multicast Data and Control Queues.
dellNetFpIngPgBuS
napshotTable
This table fetches the BST statistics at the Ingress Port for the Shared Cells, and the Headroom cells used per
Priority Group. The snapshot of the Ingress Shared cells used and the Ingress Headroom cells used per Priority
Group, when PFC is enabled, display in this table. This table lists the stack-unit index, port number and the priority
group number.
Data Center Bridging (DCB) 283