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When determining bandwidth use in campus
networks, many network administrators simply put as much bandwidth
as possible in the uplinks from the access layer to the distribution
layer and from the distribution layer to the core layer. In general,
aggregate bandwidth of the access-layer devices should not exceed
the bandwidth of the link they use to reach the distribution-layer
switch. Further, the aggregate of all uplinks to the distribution
switches should not exceed the bandwidth of the links to the core
layer. These rules will help avoid a "bottleneck"
situation where one link is overloading another link.
The following list outlines the
traffic characteristics of the sample network. 
- Eighty percent of the user traffic
remains local to the floor.
- Twenty percent of the traffic must
cross the core and reach the e-mail server.
- If all users simultaneously
accessed the network, the switch would receive 24 ports x 4
Mbps, yielding an aggregate bandwidth of 96 Mbps.
Table
outlines these statistics.
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