3Com 3CDSG8-US User Guide - Page 36

Flow Control, Storm Control

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36 Ports Information page indicate that the link is down when there is a cable connecting a device to the switch). Note: Auto causes the switch to negotiate the link speed and duplex settings with the connected device; this is called Auto-negotiation. All of the other settings cause Autonegotiation to be turned off. Note: In full-duplex mode, both ends of a connection can send traffic at the same time which effectively doubles the available throughput. In half-duplex mode, only one end of the connection can send traffic at any one time. 5.1.3 Flow Control When Flow Control is selected on a port (by clicking on the tick-box in the Flow Control column), the switch will attempt to slow incoming traffic down when traffic levels are high. It does this by sending special Pause packets on full-duplex connections or creating back-pressure (deliberately causing collisions) on half-duplex connections. This can increase traffic throughput by reducing the number of dropped packets and, as a result, the number of resends that are required. However it is not appropriate in all circumstances. 5.2 Storm Control This page allows you to set up a threshold for incoming broadcast and multicast packets. Too many incoming packets can severely cripple the switch and network performance. Rate limiting protects the switch and network by keeping the amount of data passing through the ports to a safe limit. The use of VLANs and Trunks to partition ports and network devices into separate

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36
Ports
Information
page indicate that the link is down when there is a cable connecting a device to
the switch).
Note: Auto
causes the switch to negotiate the link speed and duplex settings with the
connected device; this is called Auto-negotiation. All of the other settings cause Auto-
negotiation to be turned off.
Note:
In full-duplex mode, both ends of a connection can send traffic at the same time which
effectively doubles the available throughput. In half-duplex mode, only one end of the
connection can send traffic at any one time.
5.1.3
Flow Control
When
Flow Control
is selected on a port (by clicking on the tick-box in the
Flow Control
column), the switch will attempt to slow incoming traffic down when traffic levels are high. It
does this by sending special Pause packets on full-duplex connections or creating back-pressure
(deliberately causing collisions) on half-duplex connections. This can increase traffic throughput
by reducing the number of dropped packets and, as a result, the number of resends that are
required. However it is not appropriate in all circumstances.
5.2
Storm Control
This page allows you to set up a threshold for incoming broadcast and multicast packets. Too
many incoming packets can severely cripple the switch and network performance. Rate limiting
protects the switch and network by keeping the amount of data passing through the ports to a
safe limit. The use of VLANs and Trunks to partition ports and network devices into separate