Priority-Based Flow Control Using Dynamic Buffer Method; Pause And Resume Of Traffic; Buffer Sizes For Lossless Or Pfc Packets - Dell S4048–ON Configuration Manual

Step Task
Return to interface configuration mode.
4
Apply the DCB map, created to disable the PFC
5
operation, on the interface
Configure the port queues that still function as no-drop
6
queues for lossless traffic. For the dot1p-queue
assignments.
The maximum number of lossless queues globally
supported on a port is 2.
You cannot configure PFC no-drop queues on an
interface on which a DCB map with PFC enabled has
been applied, or which is already configured 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 configured.

Priority-Based Flow Control Using Dynamic Buffer Method

Priority-based flow control using dynamic buffer spaces is supported on the platform.
In a data center network, priority-based flow control (PFC) manages large bursts of one traffic type in multiprotocol links so that it
does not affect other traffic types and no frames are lost due to congestion. When PFC detects congestion on a queue for a
specified priority, it sends a pause frame for the 802.1p priority traffic to the transmitting device.

Pause and Resume of Traffic

The pause message is used by the sending device to inform the receiving device about a congested, heavily-loaded traffic state that
has been identified. 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
traffic when the congestion eases and reduces. The time period that is specified in the pause frame defines the duration for which
the flow 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 buffer to be less than the threshold
value and restarts the acceptance of data packets.
Dynamic ingress buffering enables the sending of pause frames at different thresholds based on the number of ports that experience
congestion at a time. This behavior impacts the total buffer size used by a particular lossless priority on an interface. The pause and
resume thresholds can also be configured dynamically. You can configure a buffer size, pause threshold, ingress shared threshold
weight, and resume threshold to control and manage the total amount of buffers that are to be used in your network environment.

Buffer Sizes for Lossless or PFC Packets

You can configure up to a maximum of 4 lossless (PFC) queues. By configuring 4 lossless queues, you can configure 4 different
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 file transfers. You can configure the
amount of buffer space to be allocated for each priority and the pause or resume thresholds for the buffer. This method of
configuration enables you to effectively manage and administer the behavior of lossless queues.
252
Data Center Bridging (DCB)
Command
exit
dcb-map {name | default}
pfc no-drop
queuesqueue-range
Command Mode
DCB MAP
INTERFACE
INTERFACE