Planex FW-100TX, Руководство пользователя

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FW-100TX
The network adapter also supports Flow Control feature for preventing
packets from overflowing the packet buffer. The flow control technology
used in half-duplex mode is called "Back Pressure", while flow control used
in full-duplex operation is called "IEEE 802.3x". In Back Pressure, a
collision signal is sent out whenever the packet buffer becomes full. On the
other hand, a switching hub with IEEE 802.3x support transmits a "pause"
command to the source node to stop the data flow itself. To utilize
IEEE802.3x flow control, the attached network card must also support
IEEE802.3x flow control. (Currently, most of the network cards on the
market do not support this feature. PCI's FNW-9800-T and FW- 1 0 0 T X
comply with IEEE802.3x flow control ahead of other vendors.)
If either the switch or network interface card does not support flow control,
the source device (PC) will continue to send packets to the switch even
when its packet buffer is full. As a result, packets received by the switch
will overflow and those overflowed packets are lost. Upper layer protocols
handle the lost packets, and TCP/IP (as one of the protocols) requests the
PC to resend the packets. Since packet overflow itself at the switch persists,
PCs will be forced to consume extra system resources by sending packets
again and again even though most of the packets are lost continuously.
About-Flow Control