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FORE Systems ES-2810 Ethernet Switch User’s Manual
Concepts in Switching
A.1 Forwarding Modes
A.1.1 Forwarding Mode Affect on Latency
Latency is the delay measured from the time the packet first enters a network device until it
leaves it. The closer a device is to zero latency, the better.
The type of network can affect latency. Over wide area networks, latency is negligible in com-
parison to the time it takes the signals to travel over long distance lines. On local area net-
works, reducing latency normally increases performance.
Unfortunately, reducing the latency can often lead to an increase in errors on the network. The
ideal situation is
Change the forwarding modes to provide added reliability and flexibility. For example, if you
are concerned about the generation of errors on a network, you can configure the ports to
store-and-forward mode to ensure safe transfer of data.
A.1.2 Possible Forwarding Modes
You can specify one of four possible forwarding modes you can specify for each port:
• Cut-through
• Fragment-free
• Store-and-forward
•Adaptive
A.1.3 Forwarding Policy
If two communicating ports (receive port and transmit port) have different forwarding modes,
then they use the “safest” mode. For example, if one port is configured for fragment-free and
the other port is configured for store-and-forward, then traffic between the two ports in either
direction is always switched using store-and-forward.
A.1.4 CRC Errors
Cyclic Redundancy Check (CRC) errors are the sum of Frame Check Sequences, longs, very
longs, alignment errors and jabbers.
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