Threshold Settings - Dell Force10 S4810P Configuration Manual

Ethernet Pause Frames allow for a temporary stop in data transmission. A situation may arise where a
sending device may transmit data faster than a destination device can accept it. The destination sends a
PAUSE frame back to the source, stopping the sender's transmission for a period of time.
The globally assigned 48-bit Multicast address 01-80-C2-00-00-01 is used to send and receive pause
frames. To allow full duplex flow control, stations implementing the pause operation instruct the MAC to
enable reception of frames with destination address equal to this multicast address.
The PAUSE frame is defined by IEEE 802.3x and uses MAC Control frames to carry the PAUSE
commands. Ethernet Pause Frames are supported on full duplex only . The only configuration applicable to
half duplex ports is
Note that if a port is over-subscribed, Ethernet Pause Frame flow control does not ensure no loss behavior.
The following error message appears when trying to enable flow control when half duplex is already
configured:
Can't configure flowcontrol when half duplex is configure, config ignored.
The following error message appears when trying to enable half duplex and flow control configuration is
on:
Can't configure half duplex when flowcontrol is on, config ignored.

Threshold Settings

Threshold Settings
When the transmission pause is set (
Ethernet Pause Frames flow control can be triggered when either the flow control buffer threshold or flow
control packet pointer threshold is reached. The thresholds are:
• Number of flow-control packet pointers: 1-2047 (default = 75)
• Flow-control buffer threshold in KB: 1-2013 (default = 49KB)
• Flow-control discard threshold in KB: 1-2013 (default= 75KB)
The pause is started when
When the discard threshold is met, packets are dropped.
The pause ends when
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 S-Series.
The discard threshold should be larger than the buffer threshold so that the buffer holds at least hold at least
3 packets.
506
| Interfaces
.
rx off tx off
are supported only on platforms:
), 3 thresholds can be set to define the controls more closely.
tx on
the packet pointer or the buffer threshold is met (whichever is met first).
either
the packet pointer and the buffer threshold fall below 50% of the threshold
both
c s