Allied-telesis AT-S20 Manuale Utente Scaricare il pdf (Pagina 53)

AT-S20 User’s Guide

4-23

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This feature is available for the XL versions only. For backpressure to

be implemented, the ports must be in half-duplex mode.

Backpressure is useful when a port’s input buffer is running low on of

memory resources. For example, outbound packets are traversing a

single uplink port. When backpressure is enabled, the switch

simulates a collision when its input buffers are nearly filled so that

sending devices will defer transmissions. These sending devices will

retry transmissions according to the Ethernet back-off algorithm.

Once switch resources are available again, the switch stops sending

the collision signals and devices can freely transmit again. Figure 4-2

shows backpressure enabled.

Figure 4-2

Enabling Backpressure

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Allied-telesis AT-S20 Manuale Utente Pagina 53