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Fast Ethernet Switching System User’s Guide
Managing the DES-5024
44
System Rate Control
The System Rate Control panel, displayed in Figure 23, allows you to set the packet
forwarding rate on the DES-5024. There are two options: Store & Forward and Cut-
Through.
Figure 23: System Rate Control
The DES-5024 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-5024 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-5024 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