3com 3CDSG8 用户指南

Trunks  

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The Speed and Duplex settings for the trunk are set by a single drop-down list. The possible 
values are: 

•  Auto - Speed and duplex settings are auto-negotiated.  
•  10HDX - 10 Mbps, half-duplex  
•  10FDX - 10 Mbps, full-duplex  
•  100HDX - 100 Mbps, half-duplex  
•  100FDX - 100 Mbps, full-duplex  
•  1000FDX - 1000 Mbps, full-duplex  

Note: Auto is the default setting and need not be changed unless you are experiencing 
problems establishing link with a connected device (i.e. the front-panel LEDs or SYSTEM > 
Information page indicate that the link is down when there is a cable connecting a device to 
the switch). 

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. 

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.