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Chapter 1: Design Overview
Foundation TopicsDesigning an internetwork requires a certain mix of art and science. Design purists can spend hours debating the merits of one design versus another, but in the real world, issues of selfinterest, background, pride, politics, and personal ego sometimes play a role in the acceptance of the design process.
For test purposes, the CCDP candidate need only be concerned with matching the business and technical requirements to the engineering, availability, time, and cost constraints. The successful network design marries the best technical solution with the needs of the business.
With the advent of e-commerce and e-business, companies face increasingly complex challenges to deliver profit to the, shareholders and value, to the customers. Their requirements for network performance are becoming more and more demanding. Add those requirements to the changing technical issues of the day, and it is easy to see why the task of CCDP is a very demanding professional assignment. In addition to having a strong technical foundation, the CCDP must articulate technical ideas to a primarily nontechnical audience. The CCDP must display a great deal of versatility. Indeed, through the life cycle of a network design, the CCDP can expect to serve in the role of project manager, consultant, integrator, technical liaison, troubleshooter, and problem solver.
Defining the ProblemA design cannot provide an effective solution to a problem that has not been defined. The CCDP who attempts to design a network before the problem is understood will be as successful as a painter who attempts to paint a moving bus. The design will never satisfy the customer, because there is no general agreement on what was needed in the first place.
No problem-no solution!
Know problem-know solution!
The CCDP's first mission is to define the problem. All design requests start with a problem as perceived by someone.
After the problem has been defined, the business requirements must be stated and needs must be prioritized. Then a technical solution can be implemented. A good network design is optimized to meet the requirements of the business at hand. Therefore, a design that is ideal for one business might be woefully lacking for another. One business might have higher security concerns, and another business might be more concerned about disaster recovery. Still another business might share these concerns but might not have the available funds to implement those features. For each client, there is an optimum design that provides a best-fit solution for his or her situation and circumstances.
Internetwork Design GoalsDesigning an internetwork can be a challenging task. Despite improvements in equipment performance and media capabilities, internetwork design is becoming more difficult. The trend is toward increasingly complex environments involving multimedia, multiple protocols, and interconnections to networks beyond an organization's domain of control. To render a successful design, the CCDP must realize stated objectives while designing the internetwork.
Here are the goals of internetwork design:
The foremost goal of an internetwork design is a working system that meets a client's business and technical objectives. Of all the goals listed, there can be no flexibility on this one. The design's success will ultimately be measured by whether the network works. The design should ensure adaptability and compatibility between old and new technologies. The design should allow scalability and flexibility as the client's business and technical requirements change. Although the design should be efficient, it should also be predictable enough to allow others to manage and troubleshoot. Even though the CCDP will understandably want to display brilliance when designing the network, it is important to keep in mind that the network design must be straightforward enough for other network personnel to grasp its concepts.
Of all the goals listed, the one the other goals must be compared is cost. The CCDP must always strike a balance with the other goals in regard to cost. In a perfect world, network design would allow each user to have voice, video, and data on the desktop. Companies, which have profit as one of their business requirements, would not want to use the fastest technology available if the price was unreasonable. The CCDP must be careful to consider cost as the most important metric. An extravagant design might look good on the dream board but, when implemented, would be wasteful and could represent a stranded investment.
If the design meets the criteria for functionality, scalability, and technological advancement while satisfying the all-important metric of cost, the design should be considered a success.
Seven Steps for Designing InternetworksFigure 1-2 shows a recommended methodology for designing a network. The first three steps should remain static, but the remaining steps will require revisions as dictated by the business's changing needs and requirements.
The following steps are recommended for designing internetworks:
- Gather information
- Analyze requirements
- Develop the internetwork structure
- Estimate network performance
- Assess costs and risks
- Implement and monitor the network
Gather InformationThe first step in network design should involve data gathering. Learn about the corporate structure. Find out what applications are being used and what plans exist in the future for change. Obtain a baseline of current network performance. Determine who will play a key role in the decision-making process. Find out how the customer assigns authority with regard to information resources. Do your best to understand the customer and their needs.
The best source of information about performance requirements is the people who use the system. Be sure to include user groups to ensure that no one is left out of the design process.