Users Guide

PFC on priority level.
Queue : 0 0 0 1 2 3 3 3 -> On Egress interface[Port B] we used no-drop queues.
Lossless trac egresses out the no-drop queues. Ingress 802.1p trac from PFC-enabled peers is automatically mapped to the no-drop
egress queues.
When conguring lossless queues on a port interface, consider the following points:
• By default, no lossless queues are congured on a port.
• A limit of two lossless queues is supported on a port. If the number of lossless queues congured exceeds the maximum supported limit
per port (two), an error message is displayed. Recongure the value to a smaller number of queues.
• If you congure lossless queues on an interface that already has a DCB map with PFC enabled (pfc on), an error message is displayed.
Table 16. Conguring Lossless Queues on a Port Interface
Step Task Command Command Mode
1 Enter INTERFACE Conguration mode.
interface
{tengigabitEthernet slot/
port | fortygigabitEthernet
slot/port}
CONFIGURATION
2
Open a DCB map and enter DCB map conguration mode.
dcb-map name
INTERFACE
3
Disable PFC.
no pfc mode on
DCB MAP
4
Return to interface conguration mode.
exit
DCB MAP
5
Apply the DCB map, created to disable the PFC operation,
on the interface
dcb-map {name | default}
INTERFACE
6
Congure the port queues that still function as no-drop
queues for lossless trac. For the dot1p-queue
assignments.
The maximum number of lossless queues globally supported
on a port is 2.
You cannot congure PFC no-drop queues on an interface
on which a DCB map with PFC enabled has been applied,
or which is already congured for PFC using the pfc
priority command.
Range: 0-3. Separate queue values with a comma; specify a
priority range with a dash; for example: pfc no-drop queues
1,3 or pfc no-drop queues 2-3 Default: No lossless queues
are congured.
pfc no-drop
queuesqueue-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
Data Center Bridging (DCB)
241