Black Box LPH240A-H, Operation Manual

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Chapter 2: Introduction
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Another feature implemented in LPH240A Series Edge
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 LPH240A Series PoE
Edge Switches varies with the port-speed types. The length of the frame
is a variable as it is with all store-and-forward switches. For 10 Mb-to-10
Mb, 10 Mb-to-100Mb or 100Mb-to-10 Mb forwarding, the latency is 15
microseconds plus the packet time of 10 Mb. For 100Mb-to-100Mb
forwarding, the latency is 5 microseconds plus the packet time of 100Mb.