Understanding the network.pdf - Back to Home

upgrade. So, when the time comes to actually design the network and deploy
it from the ground up, it is essential that you have some accurate
understanding of how the old network functions.
• Until the users are on the new network, however, using the new servers, and
so on, no real method for verifying the suitability of the design exists. It is
possible, though, to run test simulations and performance baselines on
gateways, WAN links, and servers before they are moved into production, to
examine their behavioral characteristics. Then, after the network is in
production, you can test data for comparison to your initial production
baseline.
• Verify that your network design has been implemented properly. Unless you
have installed the entire network yourself, (which is just not possible in large
network implementations), you cannot be sure that all the configurations will
be error free. In many cases, an initial performance baseline will usually
reveal any configuration or implementation problems.
• Measure the effects of a topology or hardware addition upgrade. As
mentioned above, any change to the network can have a positive or negative
effect on the overall performance. As network changes are implemented,
their effects need to be evaluated. Quite often, a change can have both
positive and negative effects; with thorough testing, these effects can be
isolated and corrected.
• Maximize the utilization of your WAN and Internet links. The
telecommunication circuits used for WAN and Internet links are quite
expensive. Evaluating their utilization can help you determine if your link is
too small or not large enough.
Ideally, any baseline study will last usually two or more days, depending on the
number of Layer 2 segments you need to sample. Before the use of network
switching became popular, baselining was straightforward. Now, to get a truly
accurate picture of network performance sampling, you need to analyze each
segment. Switches discard runts and jabbers and influence the behavior of Layer 3
broadcasts.
In selecting a baselining period, you should take into account the time of the month
that you are conducting the study. For example, if your business is calendar- driven,
and at the end of every month the network is swamped with everyone using email
and database applications to meet deadlines, this is when you want to run your
baseline. This same approach should be used to pick your sampling times. If the
office opens at 8:00, start your first sample at 8:30, when everyone is checking
email and getting started for the day. After lunch is also another prime sampling
period. Another approach is to take random samples every hour. Moreover, if you
run your backups at night over the network, be sure to collect samples during this
period as well. Deciding how and when to take your samples is largely dependent on
how the network is used. If your business is a "9 to 5" shop, some well-timed