White Papers

Command
History
Version Description
9.7(0.0) Introduced on the Z9500.
Usage
Information
Configure the maximum buffer available for PFC traffic. You can choose to increase or decrease the
buffer size that is allocated in the system by default. However, if you modify the PFC buffer size to
be lower than the previously configured PFC buffer size, the system determines whether this reduction
in size is valid without disrupting the existing configuration. In such a scenario, disable and re-enable
DCB. For example, if you modify the total buffer size to be 4000 KB from the previous size of 5000
KB, an error message is displayed that this reduction cannot be performed owing to existing system
configuration because of queues that are being currently processed.
The lossless queue limit per port is validated based on the dcb pfc-queues command. PFC queue
configuration identifies the maximum number of queues a port can support. Although the queue limit
per port is a baseline when dynamic buffering is enabled, the limit per port for queues depends on the
availability of the buffer.
Example
Dell(conf)#dcb pfc-total-buffer-size 5000 Dell(conf)#dcb pfc-total-buffer-
size 4000 %ERROR: Total pfc buffer size configured cannot accommodate
existing buffer requirement in the system.
dcb pfc-queues
Configure the number of PFC queues.
Syntax
dcb pfc-queues value
Parameters
value Enter the number of PFC queues in the range of 0 through 4. The number of ports
supported based on lossless queues configured will depend on the buffer.
Default The default number of PFC queues in the system is 2 for S4810 and 1 for S6000 platforms.
Command Modes CONFIGURATION mode
Command
History
Version Description
9.7(0.0) Introduced on the Z9500.
Usage
Information
You can configure up to a maximum of four lossless (PFC) queues. By configuring four lossless queues,
you can configure four 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.
Example
Dell(conf)#dcb pfc-queues 4
dcb <ets | pfc> enable
Enable priority flow control or enhanced transmission selection on interface.
Syntax
dcb <ets | pfc> enablepfc >enable
● To disable ETS on interface, use “no dcb ets enable” command.
● To disable PFC on interface, use “no dcb pfc enable” command.
Defaults Enable
Command Modes INTERFACE
Data Center Bridging (DCB) 527