Users Guide

Step Task Command Command Mode
Dell(config-if-te-1/1/1)# dcb-map
SAN_A_dcb_map1 Repeat Steps 1 and 2 to apply a DCB map
to more than one port.
You cannot apply a DCB map on an interface that has been
already congured for PFC using thepfc priority
command or which is already congured for lossless queues
(pfc no-drop queues command).
Conguring PFC without a DCB Map
In a network topology that uses the default ETS bandwidth allocation (assigns equal bandwidth to each priority), you can also enable PFC
for specic dot1p-priorities on individual interfaces without using a DCB map. This type of DCB conguration is useful on interfaces that
require PFC for lossless trac, but do not transmit converged Ethernet trac.
Table 15. Conguring PFC without a DCB Map
Step Task Command Command Mode
1 Enter interface conguration mode on an Ethernet port.
interface {tengigabitEthernet
slot/port |
fortygigabitEthernet slot/port}
CONFIGURATION
2 Enable PFC on specied priorities. Range: 0-7. Default:
None.
Maximum number of lossless queues supported on an
Ethernet port: 2.
Separate priority values with a comma. Specify a priority
range with a dash, for example: pfc priority 3,5-7
1 You cannot congure PFC using the pfc priority
command on an interface on which a DCB map has
been applied or which is already congured for lossless
queues (pfc no-drop queues command).
pfc priority priority-
range
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.
Data Center Bridging (DCB)
235