Users Guide

The default dot1p priority-queue assignments are applied as follows:
Dell(conf)#do show qos dot1p-queue-mapping
Dot1p Priority : 0 1 2 3 4 5 6 7
Queue : 1 0 2 3 4 5 6 7
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 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.
When trac congestion occurs, PFC sends a pause frame to a peer device with the CoS priority values of the trac that is to be stopped.
Data Center Bridging Exchange protocol (DCBx) provides the link-level exchange of PFC parameters between peer devices. PFC allows
network administrators to create zero-loss links for Storage Area Network (SAN) trac that requires no-drop service, while retaining
packet-drop congestion management for Local Area Network (LAN) trac.
To congure PFC, follow these steps:
1 Create a DCB Map.
CONFIGURATION mode
dcb-map dcb-map-name
The dcb-map-name variable can have a maximum of 32 characters.
2 Create a PFC group.
CONFIGURATION mode
priority-group group-num {bandwidth bandwidth | strict-priority} pfc on
The range for priority group is from 0 to 7.
Set the bandwidth in percentage. The percentage range is from 1 to 100% in units of 1%.
Committed and peak bandwidth is in megabits per second. The range is from 0 to 40000.
Committed and peak burst size is in kilobytes. Default is 50. The range is from 0 to 10000.
The pfc on command enables priority-based ow control.
3 Specify the dot1p priority-to-priority group mapping for each priority.
priority-pgid dot1p0_group_num dot1p1_group_num ...dot1p7_group_num
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.
Dell Networking OS Behavior: As soon as you apply a DCB policy with PFC enabled on an interface, DCBx starts exchanging information
with PFC-enabled peers. The
IEEE802.1Qbb, CEE, and CIN versions of PFC Type, Length, Value (TLV) are supported. DCBx also validates
PFC congurations that are received in TLVs from peer devices.
Data Center Bridging (DCB)
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