10/100 Auto Negotiation Switch User’s Guide
Managing the DES-3216
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System Rate Control
The System Rate Control panel, displayed in Figure 13, allows you to set the packet
forwarding rate on the DES-3216. There are two options: Store & Forward and Cut-Through.
Figure 13: System Rate Control
The DES-3216 can be set for Store and Forward or Cut-Through. This is a global setting that
affects all the ports except the RS-232 port.
Store and Forward means that when the DES-3216 receives an incoming packet it “stores”
the packet until the entire data packet has been received before it “forwards” the packet to a
destination.
In Cut-Through mode the DES-3216 begins sending out the packet as soon as it receives the
first 128 bytes of data. The first 128 bytes contain the destination of the packet.
Advantages of Store and Forward
Store and Forward only sends out valid data packets. Bad packets created by collisions on the
network or damaged packets are filtered out.
Always use Store and Forward when some devices on the network run at 10 Mbps and others
run at 100 Mbps.
Disadvantages of Store and Forward
Store and Forward requires more time because it receives the whole packet before sending it
out. Every byte buffered is an additional eight microseconds of delay. For example, 1500
