Logical vs physical design
...etwork. Either way, one should gather information about several important factors before beginning the logical design. For example, depending on the services that will be provided to clients, you might need to analyze the possible traffic patterns that might result from your plan. Locate potential bottlenecks and, where possible, alleviate them by providing multiple paths to resources or by putting up servers that provide replicas of important data so that load balancing can be provided. Considerations Who are the clients? What are their actual needs? How have you determined these needs—from user complaints or from help-desk statistics? Is this data reliable? What kinds of services will you provide on the network? Are they limited in scope? Will any involve configuring a firewall between LANs? And if so, that still doesn't account for configuring a firewall to enable access to the Internet. Will you need to allow an Internet connection for just your internal network's users, or will use you need to allow outside vendors access to your network? What will it cost to evaluate what kind of services user groups need to access from the Internet? Will you need to allow all users to use email—both within the internal network and through the firewall on the Internet? The same goes for what sites users will be allowed to access using a network browser and other network applications. Will you have users who work from home and require dial-in or VPN access through the Internet? Physical Design Physical design is the process of describing components, services, and technologies of the computer network. The purpose of the physical design is to apply real-world technology constraints to the logical model, including implementation and performance considerations. The output of the physical design process is a set of components, user interface design for a particular platform, and a physical database design. Physical design provides the basis for the functional specification and can be used as a basis for quality assurance. Considerations First one must determine their needs. What services must you provide to your user community? What are the resources you will need? If you have to compromise, what will it take to satisfy the most users or to provide the more important services? You then will have to take into account network protocols, applications, network speed, and, most important, network security issues; each of these figures into a network's logical design. Another important factor your management will probably force one to consider is cost. These factors make up the logical design for your network. You first should decide what you ...