S14 Convenient Switches
Installation and User Guide (06/04)
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While other switching technologies such as "cut-through" or "express" impose
minimal frame latency, they will also permit bad frames to propagate out to the Ethernet
segments connected. The "cut-through" technique permits collision fragment frames,
which are a result of late collisions, to be forwarded to add to the network traffic. Since
there is no way to filter frames with a bad CRC (the entire frame must be present in order
for CRC to be calculated), the result of indiscriminate cut-through forwarding is greater
traffic congestion, especially at peak activity. Since collisions and bad packets are more
likely when traffic is heavy, the result of store-and-forward operation is that more
bandwidth is available for good packets when the traffic load is greatest.
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
