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Clearing Up Network Congestion

Multiple active paths

Using path metrics, routers can make informed

routing decisions. This allows routers to have more than one active path
between networks. Multiple paths can provide load balancing, which pro-
vides more bandwidth to remote networks as well as redundancy.

To provide these advantages, routers must be more complex and more

software intensive than bridges. Routers provide a lower level of perfor-
mance in terms of the number of frames or packets that can be processed
per unit.

Segmentation with LAN Switches

LAN switching is a great strategy for LAN segmentation. LAN switches
improve performance by employing Layer 2 frame switching, which permits
high-speed data exchange.

Just like bridges, switches use the destination MAC address to ensure that

the packet is forwarded to the right outgoing port. Cut-through switches
begin forwarding the packet before reception is complete, keeping latency to
a minimum. Store-and-forward switching receives the entire frame onto its
onboard buffers, runs a CRC, and then forwards the frame out the destina-
tion port.

There are three different switching-method terms:

Port configuration-switching

Allows a port to be assigned to a physical

network segment under software control. It's the simplest form of switching.

Frame-switching

Increases available bandwidth on the network. Frame-

switching allows multiple transmissions to occur in parallel. This is the
type of switching performed by all Catalyst switches.

Cell-switching (ATM)

Uses small, fixed-length cells that are switched

on the network, similar to frame-switching. It's the switching method
used by all Cisco Lightstream switches.

A LAN switch supplies you with considerably higher port density at a

lower cost than standard bridges. Since the largest benefit of LAN switches
is fewer users per segment, the average available bandwidth per user
increases. This fewer-users-per-segment trend is known as

microsegmenta-

tion

, which lets you create dedicated segments. When you have one user per

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