GarrettCom 6K25 Manual De Usuario

Magnum 6K25 Managed Fiber Switch            Installation and User Guide (04/06) 

 

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NOTE  –  Some NIC cards only auto-negotiate when the computer system 

LINK – enabled” rule above, but may be occasionally encountered. 

 

 

When operating in 100Mb half-duplex mode, cable distances and hop-counts 

may be limited within that collision domain. The Path Delay Value (PDV) bit-times must 

account for all devices and cable lengths within that domain. For Magnum 6K25 Fast 

Ethernet switched ports operating at 100Mb half-duplex, the bit time delay is 50BT. 

 Magnum 6K25 Switches incorporate a flow-control mechanism for Full-

Duplex mode. The purpose of flow-control is to reduce the risk of data loss if a long 

burst of activity causes the switch to save frames until its buffer memory is full. This is 

most likely to occur when data is moving from a 100Mb port to a 10 Mb port and the 

10Mb port is unable to keep up. It can also occur when multiple 100Mb ports are 

attempting to transmit to one 100Mb port, and in other protracted heavy traffic situations.  

Magnum 6K25 Switches implement the 802.3x flow control (non-blocking) on 

Full-Duplex ports, which provides for a “PAUSE” packet to be transmitted to the sender 

when the packet buffer is nearly filled and there is danger of lost packets. The 

transmitting device is commanded to stop transmitting into the 6K25 Switch port for 

sufficient time to let the Switch reduce the buffer space used. When the available free-

buffer queue increases, the Switch will send a “RESUME" packet to tell the transmitter 

to start sending the packets. Of course, the transmitting device must also support the 

802.3x flow control standard in order to communicate properly during normal operation. 

Note: When in Half-Duplex mode, the 6K25 Switch implements a 

back-pressure algorithm on 10/100 Mb ports for flow control. That is, the 
switch prevents frames from entering the device by forcing a collision indication 
on the half-duplex ports that are receiving. This temporary “collision” delay 
allows the available buffer space to improve as the switch catches up with the 
traffic flow.