Users Guide

dot1p Value in
the Incoming
Frame
Egress Queue Assignment
7 3
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
Data Center Bridging: Default Conguration
Before you congure PFC and ETS on a switch see the priority group setting taken into account the following default settings:
DCB is enabled.
PFC and ETS are globally enabled by default.
The default dot1p priority-queue assignments are applied as follows:
NOTE: Although, each port on the S4810, S4820T, and S5000 devices support 8 QoS queues, you can congure only 4
QoS queues (0-3) to manage data trac. The remaining 4 queues (4-7) are reserved for control trac.
Dell(conf)#do show qos dot1p-queue-mapping
Dot1p Priority : 0 1 2 3 4 5 6 7
Queue : 0 0 0 1 2 3 3 3
Dell(conf)#
NOTE: In Egress queue assignment (8 queues in S6000 and Z9500, 4 against in S5000 and S4810.
PFC is not applied on specic dot1p priorities.
ETS: Equal bandwidth is assigned to each port queue and each dot1p priority in a priority group.
To congure PFC and ETS parameters on an S6000 interface, you must specify the PFC mode, the ETS bandwidth allocation for a
priority group, and the 802.1p priority-to-priority group mapping in a DCB map. No default PFC and ETS settings are applied to
Ethernet interfaces.
Conguring Priority-Based Flow Control
Priority-Based Flow Control (PFC) provides a ow control mechanism based on the 802.1p priorities in converged Ethernet trac
received on an interface and is enabled by default when you enable DCB.
As an enhancement to the existing Ethernet pause mechanism, PFC stops trac transmission for specied priorities (Class of
Service (CoS) values) without impacting other priority classes. Dierent trac types are assigned to dierent priority classes.
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Data Center Bridging (DCB)