| MultiLayer Switching (MLS) provides
high-performance hardware-based Layer 3 switching for Catalyst®
Switches. MLS switches IP and/or IPX data packet flows between subnets using
advanced application-specific integrated circuit (ASIC) switching
hardware. MLS offloads processor-intensive packet routing from network
routers.
Layer 3 protocols, such as IP, are
connectionless, delivering each packet independently of each other.
However, actual network traffic consists of many end-to-end
conversations, or flows, between users or applications.
A flow is a specific conversation,
consisting of many packets, between a network source and destination
within a specific time interval. For example, Hypertext Transfer
Protocol (HTTP) packets from a particular source to a particular
destination are a separate flow from File Transfer Protocol (FTP)
file transfer packets between the same pair of hosts. Flows may
consist of unicast or multicast traffic.
MLS is a technique used to increase
IP routing performance by handling the packet-switching and rewrite
functions in hardware. The Cisco implementation of MLS supports all
the traditional routing protocols; however, the frame forwarding and
rewrite process functions previously handled by a router have now
been moved into switch hardware. MLS moves the packet-forwarding
function traditionally handled by the router to Layer 3 switches
whenever a switched path exists.
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