Threshold Settings - Dell C9000 Series Networking Configuration Manual

If a port is over-subscribed, Ethernet Pause Frame flow control does not ensure no-loss behavior.
Restriction: Ethernet Pause Frame flow control is not supported if PFC is enabled on an interface.
Control how the system responds to and generates 802.3x pause frames on Ethernet interfaces. The default
is rx off tx off. INTERFACE mode. flowcontrol rx [off | on] tx [off | on]
Where:
rx on: Processes the received flow control frames on this port.
rx off: Ignores the received flow control frames on this port.
tx on: Sends control frames from this port to the connected device when a higher rate of traffic is received.
tx off: Flow control frames are not sent from this port to the connected device when a higher rate of traffic
is received.
Changes in the flow-control values may not be reflected automatically in show interface output. To display
the change, apply the new flow-control setting, perform a shutdown followed by a no shutdown on the
interface, and then check re-display the show interface output for the port.

Threshold Settings

When the transmission pause is set (tx on), you can set three thresholds to define the controls more closely.
Ethernet pause frames flow control can be triggered when either the flow control buffer threshold or flow
control packet pointer threshold is reached.
The following thresholds are provided:
• Number of flow-control packet pointers: from 1 to 2047 (default = 75)
• Flow-control buffer threshold in KB: from 1 to 2013 (default = 49KB)
• Flow-control discard threshold in KB: from 1-2013 (default= 75KB)
The pause is started when either the packet pointer or the buffer threshold is met (whichever is met first).
When the discard threshold is met, packets are dropped.
The pause ends when both the packet pointer and the buffer threshold fall below 50% of the threshold
settings.
The discard threshold defines when the interface starts dropping the packet on the interface. This may be
necessary when a connected device doesn't honor the flow control frame sent by the switch.
The discard threshold should be larger than the buffer threshold so that the buffer holds at least hold at least
three packets.
Interfaces 538