Owners Manual

By default the total available buffer for PFC is 6.6 MB and when you configure dynamic ingress buffering,
a minimum of least 52 KB per queue is used when all ports are congested. By default, the system enables
a maximum of two lossless queues on the S4820T platform.
This default behavior is impacted if you modify the total buffer available for PFC or assign static buffer
configurations to the individual PFC queues.
Configuring the Dynamic Buffer Method
Priority-based flow control using dynamic buffer spaces is supported on the S4820T platform.
To configure the dynamic buffer capability, perform the following steps:
1. Enable the DCB application. By default, DCB is enabled and link-level flow control is disabled on all
interfaces.
CONFIGURATION mode
dcb enable
2. Configure the shared PFC buffer size and the total buffer size. A maximum of 4 lossless queues are
supported.
CONFIGURATION mode
dcb pfc-shared-buffer-size 4000
dcb pfc-total-buffer-size 5000
3. Configure the number of PFC queues.
CONFIGURATION mode
dcb enable pfc-queues pfc-queues
The number of ports supported based on lossless queues configured will depend on the buffer. The
default number of PFC queues in the system is two for S4810 and Z9500, and one for S6000
platforms.
For each priority, you can specify the shared buffer threshold limit, the ingress buffer size, buffer limit
for pausing the acceptance of packets, and the buffer offset limit for resuming the acceptance of
received packets.
4. Configure the profile name for the DCB buffer threshold
CONFIGURATION mode
dcb-buffer-threshold dcb-buffer-threshold
5.
DCB-BUFFER-THRESHOLD mode
priority 0 buffer-size 52 pause-threshold 16 resume-offset 10 shared-
threshold-weight 7
6. Assign the DCB policy to the DCB buffer threshold profile on stack ports.
CONFIGURATION mode
Dell(conf)# dcb-policy buffer-threshold stack-unit all stack-ports all dcb-
policy-name
Data Center Bridging (DCB)
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