Designing a Network
you might find that the distribution of bandwidth across segments is poor. You want
to know in advance how you can measure and address these types of problems. You
might also find storage requirements are much higher or lower than you expected. You
need to know what to do if this happens. The point is that network design is a process,
often an iterative one. Your job as a network designer is to get as close as possible to the
needed design, and then fine-tune the design as needed.
A lot of the network design process is what you decide to make of it. There are
simple network design processes, and there are horrendously complicated processes
that involve dozens of people, complex statistical modeling, and even network
simulation software to test a planned design and see if it holds together under load. In
this chapter, you learn a relatively comprehensive process that is straightforward and
simple. Using the information in this chapter, along with a good dose of experience,
will yield a flexible network that should easily meet the needs of hundreds of users.
TIP You can't design a network of any size without plenty of experience running similar networks.
You can manage the overall process by understanding the methodology, but you can't create a good
design without hands-on experience. If you're new to networking and you are asked to design a
network, make sure you get experienced people on the team--either as consultants or as part of a
supplier-led team--and listen carefully to their advice. Listening well pays off with a design that will
work, rather than one that might look good on paper but won't hold up to actual use.
Assessing Network Needs
"Measure twice and cut once" is a common adage that conveys the importance of
planning. "Ready, fire, aim," is one that pokes fun at people who don't properly set
goals. Assessing the needs that a network must meet corresponds to taking those
measurements and aiming before you shoot.
Before you even think about any specifics--network topology; network operating
system (NOS) platform; a structure for hubs, bridges, and routers; or the grade of
wiring--you must first know what the network needs to accomplish. Doing a proper
job can be tedious, but assessing needs is where you should place the most emphasis
during a design process. Failing to do so almost certainly will result in a network that
isn't productive for its users.
NOTE Many IT professionals are, at heart, technologists who love to play with the latest
technologies. It's very tempting to design the network around the "hot" technologies, and then try
to figure out how the needs fit into those technologies. However, this is not the way to go about
designing a network. Instead, start with the needs, and then find out what technologies support