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Chapter 1

Scaling Large Internetworks

One way to solve congestion problems and increase the networking per-

formance of your LAN is to divide a single Ethernet segment into multiple
network segments, which maximizes the available bandwidth. Some of the
ways to do that are as follows:

Physical segmentation

You can segment the network with bridges and

routers, thereby breaking up the collision and broadcast domains. This
minimizes packet collisions by decreasing the number of workstations on
the same physical network.

Network switching technology (microsegmentation)

Like a bridge or

router, switches can also provide LAN segmentation capabilities. LAN
switches (for example, the Cisco Catalyst 5000) provide dedicated, point-
to-point, packet-switched connections between their ports. Since this
allows simultaneous switching of packets between the ports in the switch,
it increases the amount of bandwidth open to each workstation.

Using full-duplex Ethernet devices

Full-duplex Ethernet can provide

almost twice the bandwidth of traditional Ethernet networks. However,
for this to work, both the switch port and the network interface cards
(NICs) must be able to run in Full Duplex mode.

Using Fast or Gigabit Ethernet

Using Fast Ethernet and gigabit

switches can provide up to 100 times the amount of bandwidth available
from 10BaseT.

It's no surprise--reducing the number of users per collision domain

increases the bandwidth on your network segment. By keeping the traffic
local to the network segment, users have more bandwidth available to them
and enjoy a noticeably better response time than if there was simply one
large backbone in place.

Okay, now let's explore some different ways to clear up nasty network

congestion problems:

Segmentation with bridges

Segmentation with routers

Segmentation with switches

Segmentation with a Bridge

A bridge can segment, or break up, your network into smaller, more man-
ageable pieces. However, if it's placed incorrectly in your network, it can
cause more harm than good.

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