AT-FS716L & AT-FS724L Fast Ethernet Switch Installation Guide
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How a switch signals an end-node to stop transmitting data differs
depending on the duplex mode of the end-node and switch port. A
twisted-pair port operating in half-duplex mode stops an end-node from
transmitting data by forcing 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 an end-node to stop sending data,
wait for a brief period of time, and then retransmit the same data. Once the
switch is ready to receive data again, the switch stops forcing collisions.
This is referred to as backpressure.
A port operating in full-duplex mode uses PAUSE frames, as specified in
the IEEE 802.3x standard, to stop the transmission of data from an end-
node. Whenever the switch wants an end-node to stop transmitting data, it
issues this frame. The frame instructs the end-node to cease transmission
for a period of time specified within the frame. The switch continues to
issue PAUSE frames until it is ready again to receive data from the end-
node. This is referred to as flow control.
