Users Guide

• Specify the dot1p priority-to-priority group mapping for each priority. The priority group range is from 0 to 7. All priorities that
map to the same queue must be in the same priority group.
Leave a space between each priority group number. For example: priority-pgid 0 0 0 1 2 4 4 4 in which priority group 0 maps to
dot1p priorities 0, 1, and 2; priority group 1 maps to dot1p priority 3; priority group 2 maps to dot1p priority 4; priority group 4 maps
to dot1p priorities 5, 6, and 7.
Important Points to Remember
• If you remove a dot1p priority-to-priority group mapping from a DCB map (no priority pgid command), the PFC and ETS
parameters revert to their default values on the interfaces on which the DCB map is applied. By default, PFC is not applied on
specic 802.1p priorities; ETS assigns equal bandwidth to each 802.1p priority.
As a result, PFC and lossless port queues are disabled on 802.1p priorities, and all priorities are mapped to the same priority queue
and equally share the port bandwidth.
• To change the ETS bandwidth allocation congured for a priority group in a DCB map, do not modify the existing DCB map
conguration. Instead, rst create a new DCB map with the desired PFC and ETS settings, and apply the new map to the
interfaces to override the previous DCB map settings. Then, delete the original dot1p priority-priority group mapping.
If you delete the dot1p priority-priority group mapping (no priority pgid command) before you apply the new DCB map,
the default PFC and ETS parameters are applied on the interfaces. This change may create a DCB mismatch with peer DCB
devices and interrupt network operation.
QoS dot1p Trac Classication and Queue Assignment
The following section describes QoS dot1P trac classication and assignments.
DCB supports PFC, ETS, and DCBx to handle converged Ethernet trac that is assigned to an egress queue according to the
following QoS methods:
Honor dot1p
You can honor dot1p priorities in ingress trac at the port or global switch level (refer to Default dot1p to
Queue Mapping) using the service-class dynamic dot1p command in INTERFACE conguration
mode.
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 Networking does not recommend mapping all ingress trac to a single queue when using PFC and ETS.
However, Dell 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 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.
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.
dot1p Value in
the Incoming
Frame
Egress Queue Assignment
0 0
1 0
2 0
246
Data Center Bridging (DCB)