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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”. Th
is 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
Mb-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.