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Designing large-scale networks to meet today’s dynamic business and IT needs and
trends is a complex assignment, whether it is an enterprise or service provider type of
network. This is especially true when the network was designed for technologies and
requirements relevant years ago and the business decides to adopt new IT technologies
to facilitate the achievement of its goals but the business’s existing network was not
designed to address these new technologies’ requirements. Therefore, to achieve the
desired goal of a given design, the network designer must adopt an approach that tackles
the design in a structured manner.
There are two common approaches to analyze and design networks:
■ The top-down approach: The top-down design approach simplifies the design pro-
cess by splitting the design tasks to make it more focused on the design scope and
performed in a more controlled manner, which can ultimately help network design-
ers to view network design solutions from a business-driven approach.
■ The bottom-up approach: In contrast, the bottom-up approach focuses on select-
ing network technologies and design models first. This can impose a high potential
for design failures, because the network will not meet the business or applications’
requirements.
To achieve a successful strategic design, there must be additional emphasis on a business
driven approach. This implies a primary focus on business goals and technical objectives,
in addition to existing and future services and applications. In fact, in today’s networks,
business requirements are driving IT and network initiatives as shown in Figure 1-1 [6].
For instance, although compliance (as presented in Figure 1-1 ) might seem to be a design
constraint rather than a driver, many organizations today aim to comply with some
standards with regard to their IT infrastructure and services to gain some business advan-
tages, such as compliance with ISO/IEC 27001 Information Security Management,
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will
Network Design Requirements:
Analysis and Design Principles
Chapter 1
1. http://www.iso.org/iso/home/standards/management-standards/iso27001.htm
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