|  | 3.2 | The First Steps in WAN Design
| 3.2.1 | WAN design goals

Designing a WAN can be a challenging task. The discussions that follow outline several areas that you should carefully consider when planning a WAN implementation. The steps described here can lead to improved WAN cost and performance. Businesses can continually improve their WANs by incorporating these steps into the planning process. Two primary goals drive WAN design and implementation: Application availability - Networks carry application information between computers. If the applications are not available to network users, the network is not doing its job. Total cost of ownership - Information Systems (IS) department budgets often run in the millions of dollars. As large businesses increasingly rely on electronic data for managing business activities, the associated costs of computing resources will continue to rise. A well-designed WAN can help to balance these objectives. When properly implemented, the WAN infrastructure can optimize application availability and allow the cost-effective use of existing network resources. In general, WAN design needs to take into account three general factors: Environmental variables - Environmental variables include the location of hosts, servers, terminals, and other end nodes; the projected traffic for the environment; and the projected costs for delivering different service levels. Performance constraints - Performance constraints consist of network reliability, traffic throughput, and host/client computer speeds (for example, network interface cards and hard drive access speeds). Networking variables - Networking variables include the network topology, line capacities, and packet traffic. Characterizing network traffic is critical to successful WAN planning, but few planners perform this key step well, if at all.
| Engineering Journal
Traffic Characterization

The overall goal of WAN design is to minimize cost based on these elements while delivering service that does not compromise established availability requirements. You face two primary concerns: availability and cost. These issues are essentially at odds. Any increase in availability must generally be reflected as an increase in cost. Therefore, you must carefully weigh the relative importance of resource availability and overall cost.

The first step in the design process is to understand the business requirements, which is covered in the following sections. WAN requirements must reflect the goals, characteristics, business processes, and policies of the business in which they operate.

| Web Links
| Network Pre-Installation Guide
| Dartmouth Method for Teaching Design