Reference Guide

For DCB to operate effectively, you can classify ingress traffic according to its dot1p priority so that it maps to different
data queues. The dot1p-queue assignments used are shown in the following table.
To enable DCB, enable either the iSCSI optimization configuration or the FCoE configuration. For information to configure
iSCSI optimization, refer to Enable and Disable iSCSI Optimization. For information to configure FCoE, refer to Step 1 in
Configuring FIP Snooping.
To enable DCB with PFC buffers on a switch, enter the following commands, save the configuration, and reboot the
system to allow the changes to take effect.
1. Enable DCB.
CONFIGURATION mode
dcb enable
2. Set PFC buffering on the DCB stack unit.
CONFIGURATION mode
dcb stack-unit all pfc-buffering pfc-ports 64 pfc-queues 2
NOTE: To save the pfc buffering configuration changes, save the configuration and reboot the system.
NOTE: FTOS Behavior: DCB is not supported if you enable link-level flow control on one or more interfaces. For
more information, refer to Ethernet Pause Frames.
QoS dot1p Traffic Classification and Queue Assignment
The following section describes QoS dot1P traffic classification and assignments.
DCB supports PFC, ETS, and DCBx to handle converged Ethernet traffic that is assigned to an egress queue according to
the following QoS methods:
Honor dot1p You can honor dot1p priorities in ingress traffic at the port or global switch level (refer to
Default dot1p to Queue Mapping) using the service-class dynamic dot1p command
in INTERFACE configuration mode.
Layer 2 class
maps
You can use dot1p priorities to classify traffic in a class map and apply a service policy to an
ingress port to map traffic to egress queues (refer to Policy-Based QoS Configurations).
NOTE: Dell Networking does not recommend mapping all ingress traffic to a single queue when using PFC and ETS.
However, Dell Networking does recommend using Ingress traffic classification using the service-class
dynamic dot1p
command (honor dot1p) on all DCB-enabled interfaces. If you use L2 class maps to map dot1p
priority traffic 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 Configuring Lossless Queues).
Although FTOS allows you to change the default dot1p priority-queue assignments (refer to Setting dot1p Priorities
for Incoming Traffic), DCB policies applied to an interface may become invalid if you reconfigure dot1p-queue
mapping. If the configured DCB policy remains valid, the change in the dot1p-queue assignment is allowed.
dot1p Value in the
Incoming Frame
Egress Queue Assignment
0 0
1 0
2 0
3 1
240