Flooding; Backpressure And Flow Control - Allied Telesis AT-GS920/16 Installation And User Manual

Flooding

Backpressure and
Flow Control
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.
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.
Chapter 1: Product Description
29