GarrettCom 4K-Series Manual De Usuario

Magnum 4K8 Switches      Installation and User Guide      (10/04) 

 

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

The Magnum 4K-Series Switches perform half- or full-duplex mode auto-

negotiation independently on all switched ports. If the device or node on the other end of 

a port’s attached cable supports  auto-negotiation, the Magnum 4K8 Switch will 

negotiate to run full-duplex.  If the attached device or node doesn’t support auto-

negotiation (for example, if it is a 10 Mb repeater or a standard 10 Mb hub), the K-

Switch’s RJ-45 ports will default to operate at half-duplex. 

 Magnum 4K- Series 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 

speed difference makes the 10Mb port 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 4K-Series Fiber 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 4K8-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 indicate 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 4K8-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.