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MultiLayer Switching (MLS) combines
Layer 2 switching and Layer 3 routing functionality.
MLS moves campus traffic at wire speed while at the same time
satisfying Layer 3 routing requirements. This combination not only
solves throughput problems, but also removes the conditions under
which Layer 3 bottlenecks form. MLS is based on a "route once,
switch many" model, as shown in Figure .
This feature has become a highly
desired method of accelerating routing performance through the use
of dedicated ASICs. Traditional routing is carried out as a combined
effort between software and the CPU; MLS offloads a significant
portion of routing to hardware.
MLS can operate at Layer 3 or 4. When
operating as a Layer 3 switch, the switch caches flows based on IP
addresses. When operating as a Layer 4 switch, the switch caches
conversations based on source address, destination address, source
port, and destination port.
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