User guide

BLACK BOX

Series Convenient Switches Installation and User Guide

forwarding can occur. This technique ensures that all forwarded frames are of a valid

length and have the correct CRC, i.e., are good packets. This eliminates the propagation of

bad packets, enabling all of the available bandwidth to be used for valid information.

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.