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2.2
Flow control function
In this device, the flow control function is supported by Pause frame based on IEEE802.3x. As per the flow
control settings, operation of each port is as shown below.
Points to be noted
When the flow control is applied, the connected side might not be able to transmit the frame to corresponding
port of this device. In this case, frame may be discarded as per the buffer capacity of connected side irrespective
of the priority of priority function that is set in this device. For that, disable the flow control for the network
where voice or image is used. In addition, transfer performance of data frame may deteriorate depending on
the connected side. Whether the PAUSE frame must be transmitted by flow control, is decided as per the
remaining capacity of the received buffer of input port. The frame transferred to port that is being controlled by
the length of output queue with 'buffermode qos' or 'ratecontrol', is discarded in output queue side, therefore it
is not accumulated in the reception buffer of input port. As a result, regardless of the frame being disregarded,
'Pause' frame is not transmitted. In order to execute the flow control steadily, set the buffermode to max so
that it is not transfered to the port where the ratecontrol is set.
<In case of fixed mode>
Flow control setting
Transmission
Reception
Off setting
Off setting
On setting
Off setting
Off setting
Off setting
On setting
Off setting
1) Ignored when Pause frame is received.
Communication
mode
Transmission direction
Full double fixed
Pause frame not transmitted
Pause frame is transmitted for
Full double fixed
flow control.
Full double fixed
Pause frame not transmitted
Pause frame is transmitted for
Full double fixed
flow control.
System operation
Reception direction
Flow control is not executed when
Pause frame is received ( 1)
Flow control is not executed when
Pause frame is received ( 1)
Flow control is executed Pause frame is
received
Flow control is not executed when
Pause frame is received ( 1)
Page 6 of 71
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