Allied Telesis AT-S62 - Manual (Page 614)

Chapter 35: Port Parameters
Section VIII: Web Browser Management 614
Back Pressure
Sets backpressure on a port. This option only applies to ports
operating in half-duplex mode. A switch port uses backpressure
to control the flow of ingress packets.
When a twisted pair port on the switch operating in half-duplex
mode needs to stop an end node from transmitting data, it forces
a collision. A collision on an Ethernet network occurs when two
end nodes attempt to transmit data using the same data link at
the same time. A collision causes the end nodes to stop sending
data.
When a switch port needs to stop a half-duplex end node from
transmitting data, it forces a collision on the data link, which stops
the end node. Once the switch is ready to receive data again, the
switch stops forcing collisions. This is called backpressure.
The default setting for backpressure on a switch port is disabled.
The Limit field specifies the maximum number of ingress packets
that a port will accept within a 1 second period before initiating
backpressure. The range is 1 to 57,344. The default is 8192.
Flow Control
Sets flow control on the port. This option applies only to ports
operating in full-duplex mode.
A switch port uses flow control to control the flow of ingress
packets from its end node.
A port using flow control issues a special frame, referred to as a
PAUSE frame, as specified in the IEEE 802.3x standard, to stop the
transmission of data from an end node. When a port needs to stop
an end node from transmitting data, it issues this frame. The frame
instructs the end node to cease transmission. The port continues
to issue PAUSE frames until it is ready again to receive data from
the end node.
The default setting for flow control on a switch port is disabled.
Possible values are:
Auto - The port will use flow control if it detects that the end node
is using it.
Disabled - No flow control on the port.
Enabled - Flow control is activated.
Limit - Specifies the maximum number of ingress packets that a
port will receive within a 1 second period before initiating flow
control. The range is 1 to 57,344 packets. The default is 8192.