Documenting Your Network
This chapter starts by providing advice on responding to a customer’s request for proposal
(RFP), and concludes with information on writing a design document when no RFP exists.
The section “Contents of a Network Design Document” provides an outline of a typical
design document, and specifies the topics that should be included in each part of the docu-
ment. The section serves as a summary for Top-Down Network Design because it references
each of the major steps of the top-down design methodology presented in this book.
At this point in the design process, you should have a comprehensive design that is based
on an analysis of your customer’s business and technical goals, and includes both logical
and physical components that have been tested and optimized. The next step in the process
is to write a design document.
A design document describes your customer’s requirements and explains how your design
meets those requirements. It also documents the existing network, the logical and physical
design, and the budget and expenses associated with the project.
It is also important that a design document contain plans for implementing the network,
measuring the success of the implementation, and evolving the network design as new
application requirements arise. The network designer’s job is never complete. The process
of analyzing requirements and developing design solutions begins again as soon as a design
is implemented. Figure 14-1 shows the cyclical nature of the top-down network design
As mentioned in earlier chapters, in addition to being cyclical, network design is also
iterative. Some steps take place during multiple phases of a design. Testing occurs during
the design-validation phase and also during implementation. Optimization occurs while
finalizing the design and also after implementation during the network-monitoring phase.
Documentation is an ongoing effort. Documentation that is completed before the imple-
mentation stage can facilitate the approval process for a design and help expedite the rollout
of new technologies and applications.

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