Setup Guide

Table 19. Conguring PFC Assymetric
Step Task Command Command Mode
1 Enter interface conguration mode on an Ethernet port.
DellEMC#interface
interface-type
CONFIGURATION
2 Enable pfc asymmetric on interface.
DellEMC(conf-if-
fo-1/1/1)#pfc asymmetric
INTERFACE
3 Congure pfc storm control to disable the queue if the pfc
storm is detected
DellEMC(conf-if-
fo-1/1/1)#storm-control
pfc in queue-drop
INTERFACE
4 Clear the queue disable state, when the queue is disabled
during the pfc storm detection
DellEMC(conf-storm-
control-pcf)# storm-
control pfc in queue-
drop-state clear
INTERFACE
Priority-Based Flow Control Using Dynamic Buer
Method
In a data center network, priority-based ow control (PFC) manages large bursts of one trac type in multiprotocol links so that it does not
aect other trac types and no frames are lost due to congestion. When PFC detects congestion on a queue for a specied priority, it
sends a pause frame for the 802.1p priority trac to the transmitting device.
Pause and Resume of Trac
The pause message is used by the sending device to inform the receiving device about a congested, heavily-loaded trac state that has
been identied. When the interface of a sending device transmits a pause frame, the recipient acknowledges this frame by temporarily
halting the transmission of data packets. The sending device requests the recipient to restart the transmission of data trac when the
congestion eases and reduces. The time period that is specied in the pause frame denes the duration for which the ow of data packets
is halted. When the time period elapses, the transmission restarts.
When a device sends a pause frame to another device, the time for which the sending of packets from the other device must be stopped is
contained in the pause frame. The device that sent the pause frame empties the buer to be less than the threshold value and restarts the
acceptance of data packets.
Dynamic ingress buering enables the sending of pause frames at dierent thresholds based on the number of ports that experience
congestion at a time. This behavior impacts the total buer size used by a particular lossless priority on an interface. The pause and resume
thresholds can also be congured dynamically. You can congure a buer size, pause threshold, ingress shared threshold weight, and
resume threshold to control and manage the total amount of buers that are to be used in your network environment.
Buer Sizes for Lossless or PFC Packets
You can congure up to a maximum of 64 lossless (PFC) queues. By conguring 64 lossless queues, you can congure multiple priorities
and assign a particular priority to each application that your network is used to process. For example, you can assign a higher priority for
time-sensitive applications and a lower priority for other services, such as le transfers. You can congure the amount of buer space to be
allocated for each priority and the pause or resume thresholds for the buer. This method of conguration enables you to eectively
manage and administer the behavior of lossless queues.
Data Center Bridging (DCB)
289