Black Box LE14XXA Manual De Usuario

Black Box Modular Switches           

        Installation and User Guide (8/99) 

11 

LE14XXA-Series Switches are constantly adapting internally to provide maximum network 

performance with the least dropped packets. 

When the Switch detects that its free buffer queue space is low, the Switch sends 

industry standard (full-duplex only) PAUSE packets out to the devices sending packets to cause 

“flow control”. This tells the sending devices to temporarily stop sending traffic, which allows a 

traffic catch-up to occur without dropping packets. Then, normal packet buffering and 

processing resumes. This flow-control sequence occurs in a small fraction of a second and is 

transparent to an observer.  See Section 4.6 for additional details. 

 

Another feature implemented in LE14XXA--Series Switches is a collision-based flow

control mechanism (when operating at half-duplex only). When the Switch detects that its free 

buffer queue space is low, the Switch prevents more frames from entering by forcing a collision 

signal on all receiving half-duplex ports in order to stop incoming traffic. 

 

The latency (the time the frame spends in the Switch before it is sent along or 

forwarded to its destination) of the LE14XXA-Series Switches varies with the port-speed types, 

and the length of the frame is a variable here as it is with all store-and-forward switches. For 10 

M b-to-10 Mb or 10 Mb-to-100Mb or 100Mb-to-10 Mb forwarding, the latency is 15 

microseconds plus the packet time at 10 Mb. For 100Mb-to-100Mb forwarding, the latency is 5 

microseconds plus the packet time at 100Mb.