Users Guide

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.
NOTE: You cannot enable PFC and link-level ow control at the same time on an interface.
Conguring Lossless Queues
DCB also supports the manual conguration of lossless queues on an interface when PFC mode is turned o.
Prerequisite: A DCB with PFC conguration is applied to the interface with the following conditions:
• PFC mode is o (no pfc mode on).
• No PFC priority classes are congured (no pfc priority priority-range).
Example:
Port A —> Port B
Port C —> Port B
PFC no-drop queues are congured for queues 1, 2 on Port B. PFC capability is enabled on priorities 3, 4 on PORT A and C.
Port B acting as Egress
During the congestion, [trac pump on priorities 3 and 4 from PORT A and PORT C is at full line rate], PORT A and C send out the
PFCs to rate the trac limit. Egress drops are not observed on Port B since trac ow on priorities is mapped to loss less queues.
Port B acting as Ingress
If the trac congestion is on PORT B , Egress DROP is on PORT A or C, as the PFC is not enabled on PORT B.
Refer the following conguration for queue to dot1p mapping:
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
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Data Center Bridging (DCB)