In this chapter, you learned about design in general and specifically about network design principles. You also learned about modular network design and the hierarchical and Enterprise Composite Network models for designing networks.
As a summary of the network design process presented here, consider the following checklist:
• Did you ask probing questions to really understand the requirements?
• Have you determined the requirements and constraints related to technical issues? Are the requirements clear and deterministic (verifiable)?
• Have you determined the requirements and constraints related to business issues, including the budget? Are the requirements clear and deterministic?
• Have you prioritized, or assigned weights to, each of the requirements?
• Do you understand the network solutions/applications that are called for, and which network services are required to support them?
• Have you analyzed and audited the existing network, if one exists, to determine any restrictions on the new network as well as what portions of the existing network should be retained?
• Did you create some preliminary design options, using a top-down approach, so that all the network requirements are considered?
• Did you create a modular design?
• Did you identify the hierarchical network design layers in your design, and did you consider the appropriate devices and links for each layer?
• Did you use the Enterprise Composite Network Model in your design? Did you identify the relevant functional areas and modules of this model that will be used in your network, and did you consider the appropriate devices and links for each module?
• Did you and the network owner agree on the optimal solution, based on your preliminary design options?
• Did you implement a prototype or pilot network to verify all or a portion of the design?
• Did you create a detailed deployment plan and schedule, including implementation, testing, training, and contracts?
• Do you have a plan for what is to be monitored in the operating network and how errors are to be handled?
• Have you thoroughly documented the details of the design and the design process?
Network design is an art as well as a science. Just as there are many different ways to design an addition to a house, there are a variety of ways to design a network. It is critical to keep going back to the agreed-to requirements and their importance to the network owner; this helps ensure that the final network will be a success.
The technologies used in the network are constantlyand in some cases quicklyevolving. Because it is impossible to be an expert on all the technologies, we encourage you to seek help during your design from experts in specific fields. A good up-front design reduces the likelihood of catastrophes during the implementation or operation phases of the network life cycle.
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