Allied Telesis AT-GS920/16, Installation And User Manual

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Chapter 1: Product Description
29
Flooding
The Flooding mode allows all received legal frames to be switched through
the GS920 Series switch.
Note
The Flooding mode has a higher priority and takes precedence over
the Multicast Frame Pass-Through feature. If the Multicast Frame
Pass-Through feature is desired, then the Flooding feature must be
disabled.
This feature can be enabled or disabled by setting DIP switch # 4
(Flooding). See “Flooding” on page 80 for the procedure to enable and
disable this feature.
Note
The GS920 series switches DO NOT SUPPORT the combination of
Flooding & Flow Control. If both the flooding and flow control
features are enabled at once, traffic will be stopped by pause
packet.
For example: 1G traffic --> 10Mbps,100Mbps, then 1G traffic will be
10Mbps because of pause packet.
Backpressure and
Flow Control
To maintain the orderly movement of data between the end-nodes, an
Ethernet switch may periodically need to signal an end-node to stop
sending data. This can occur under several circumstances. For example, if
two end-nodes are operating at different speeds, the switch, while
transferring data between the end-nodes, might need to instruct the faster
end-node to stop transmitting data to allow the slower end-node to catch
up. An example of this would be when a server operating at 100 Mbps is
sending data to a workstation operating at only 10 Mbps.
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.