As network expectations have changed, so have design principles. Enterprises
no longer rely on a single vendor, technology, or protocol. The design strategy
has changed dramatically to include security and scalability as primary
criteria. Security has a large impact on network design.
There is greater
redundancy in network designs. Organizations are focusing on increased levels
of redundancy, and disaster-recovery planning is becoming a necessity.
Redundancy takes many forms, including separate power sources, multiple WAN
carriers, alternate cable routes, and redundant hardware. Network connectivity
and services are critical components of enterprise operations. The cost of
downtime is increasing at a phenomenal rate.
Designing a network is not a trivial factor. Assessing the design criteria
enables designers to understand the network and what it was meant to do.
Network designs must easily adapt to implement the next generation of
technology. Many network designers are planning for IP telephony. These network
design plans are not just for new networks but are improvements on existing
ones. Properly planning networks based on sound architecture makes necessary
network redesigns easier at a later stage.
Stages of the
Network
Design is just one component of a network life cycle. Planning,
design, implementation, operation, and optimization (PDIOO) are the stages of
the network life cycle. Each stage builds on its predecessor to create a sound
network that maintains its effectiveness despite changing business needs. The
PDIOO methodology can be applied to all technologies. During the PDIOO process,
the designer should define key deliverables and associated actions with a
direct correlation to the added value and benefit for the network. For example,
understanding business goals, usage characteristics, and network requirements
helps to avoid unnecessary upgrades and network redesigns, thereby reducing the
time it takes to introduce new services in the network.
Planning
Phase
During the planning stage, the logic of future designs can be
tested for flaws. Planning helps to avoid logical mistake being replicated in a
network design that might be used as a template across a number of locations.
The planning stage focuses on technical as well as financial criteria and takes
into account all the requirements and constraints that were discussed in the
previous section. During this phase, it is important to identify all the
stakeholders in order to make this process a success. The stakeholders are
people or organizations who have a vested interest in the environment,
performance, and outcome of the project.
Design Phase
After completing the planning stage, the designer
has enough information to develop a network design. If a network is already in
place, this phase can be used to review and validate the network design as it
is currently implemented. At this stage, products, protocols, and features are
chosen based on criteria defined in the planning stage. Network diagrams are
developed to illustrate what changes will occur in the network to achieve the
desired results. The more detailed the network diagram and plan, the easier it
will be to anticipate the challenges during implementation.
Implementation Phase
The implementation stage provides detailed,
customized deliverables to help avoid risks and meet expectations. A sound
implementation plan ensures smooth deployment even when issues arise.
Communicating the implementation plan to all stakeholders provides an
opportunity to assess the viability of the plan. It is better to find mistakes
on the drawing board than during implementation.
Good processes, such as
change control, can effectively handle issues that occur during deployment.
Change control provides flexibility because it is impossible to plan for every
contingency, especially if the implementation has a long duration.
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NOTE:
Change control is a procedure by which authorized amendments are made
to the organization's business process. It involves analyzing the problem
and appending the results to a formal proposal. This proposal should be
reviewed by management before being authorized.
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Operation Phase
The operation phase, also known as the
operational-support phase, is designed to protect the network investment and
help the staff prevent problems, maximize system utility, and accelerate
problem resolution.
Optimization Phase
The last step in the PDIOO process is the
optimization of the network. A sound design still requires optimization and
tweaking to reach its full potential. The optimization of the network can be as
simple as hardening servers against security threats or adding QoS to the
network for latency-sensitive traffic.