Concept Guide

Layer 2 class maps You can use dot1p priorities to classify trac in a class map and apply a service policy to an ingress port to map
trac to egress queues.
NOTE: Dell EMC Networking does not recommend mapping all ingress trac to a single queue when using PFC and ETS.
However, Dell EMC Networking does recommend using Ingress trac classication using the service-class dynamic
dot1p command (honor dot1p) on all DCB-enabled interfaces. If you use L2 class maps to map dot1p priority trac to egress
queues, take into account the default dot1p-queue assignments in the following table and the maximum number of two lossless
queues supported on a port
(refer to Conguring Lossless Queues).
Although Dell EMC Networking OS allows you to change the default dot1p priority-queue assignments (refer to Setting dot1p Priorities
for Incoming Trac), DCB policies applied to an interface may become invalid if you recongure dot1p-queue mapping. If the
congured DCB policy remains valid, the change in the dot1p-queue assignment is allowed.
dot1p Value in
the Incoming
Frame
Egress Queue Assignment
0 2
1 0
2 1
3 3
4 4
5 5
6 6
7 7
Conguring the Dynamic Buer Method
Priority-based ow control using dynamic buer spaces is supported on the switch.
To congure the dynamic buer capability, perform the following steps:
1 Enable the DCB application. By default, DCB is enabled and link-level ow control is disabled on all interfaces.
CONFIGURATION mode
dcb enable
2 Congure the shared PFC buer size and the total buer size. A maximum of 4 lossless queues are supported.
CONFIGURATION mode
dcb pfc-shared-buffer-size value
dcb pfc-total-buffer-size value
The buer size range is from 0 to 3399. Default is 3088.
3 Congure the number of PFC queues.
CONFIGURATION mode
dcb enable pfc-queues pfc-queues
The number of ports supported based on lossless queues congured depends on the buer. The default number of PFC queues in the
system is two.
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Data Center Bridging (DCB)