Chapter 2: Introduction
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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.
Another feature implemented in the LBH08x/LBH18x Industrial Switch 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 LBH08x/LBH18x Industrial Switch 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 Mbps-to-10 Mbps or 10 Mbps-to-100Mbps or 100Mbps-
to-10 Mbps forwarding, the latency is 15 microseconds plus the packet time at 10
Mbps. For 100Mbps-to-100Mbps forwarding, the latency is 5 microseconds plus the
packet time at 100Mbps.
