|  | 3.2 | The First Steps in WAN Design
| 3.2.2 |
The gathering requirements phase of WAN design

When designing a WAN, you need to start by gathering data about the business structure and processes. Next, you need to determine who the most important people will be in helping you design the network. You need to speak to major users and find out their geographic location, their current applications, and their projected needs. The final network design should reflect the user requirements. In general, users primarily want application availability in their networks. The chief components of application availability are response time, throughput, and reliability: Response time is the time between entry of a command or keystroke and the host system's execution of the command or delivery of a response. Applications in which fast response time is considered critical include interactive online services, such as automated tellers and point-of-sale machines. Throughput-intensive applications generally involve file-transfer activities. However, throughput-intensive applications also usually have low response-time requirements. Indeed, they can often be scheduled at times when response-time-sensitive traffic is low (for example, after normal work hours). Although reliability is always important, some applications have genuine requirements that exceed typical needs. Organizations that conduct all business activities online or over the telephone require nearly 100% uptime. Financial services, securities exchanges, and emergency, police, and military operations are a few examples. These situations require a high level of hardware and redundancy. Determining the cost of downtime is essential in determining the importance of reliability to your network. You can assess user requirements in a number of ways. The more involved your users are in the process, the more likely your evaluation will be accurate. In general, you can use the following methods to obtain this information: User community profiles-Outline what different user groups require. This is the first step in determining network requirements. Although most general users have the same requirements of e-mail, they may also have different needs such as sharing local print servers in their area. Interviews, focus groups, and surveys build a baseline for implementing a network. Understand that some groups might require access to common servers. Others might want to allow external access to specific internal computing resources. Certain organizations might require IS support systems to be managed in a particular way, according to some external standard. The least formal method of obtaining information is to conduct interviews with key user groups. Focus groups can also be used to gather information and generate discussion among different organizations with similar (or dissimilar) interests. Finally, formal surveys can be used to get a statistically valid reading of user sentiment regarding a particular service level. Human factors tests-The most expensive, time-consuming, and possibly revealing method of assessing user requirements is to conduct a test involving representative users in a lab environment. This is most applicable when you're evaluating response time requirements. For example, you might set up working systems and have users perform normal remote host activities from the lab network. By evaluating user reactions to variations in host responsiveness, you can create benchmark thresholds for acceptable performance. After gathering data about the corporate structure, you need to determine where information flows in the company. Find out where shared data resides and who uses it. Determine whether data outside the company is accessed. Make sure you understand the performance issues of any existing network. If time permits, analyze the performance of the existing network.
| Threaded Case Study
Washington Project: Understanding the Customer

First and foremost, you must understand your customers; in the case of the Washington School District, your customers include teachers, students, staff members, and administrators.

You need to determine whether the district has documented policies in place. You need to answer questions like the following:

- Has district data been declared mission critical?
- Have district operations been declared mission critical?
- What protocols are allowed on the district network?
- Are only certain desktop hosts supported in the district?

Mission-critical data and operations are considered key to the business, and access to them is critical to the business running on a daily basis. You need to determine who in the district has authority over mission-critical data and operations, along with addressing, naming, topology design, and configuration. Some districts have a central Management Information System (MIS) department that controls everything. Some districts have very small MIS departments and, therefore, must pass on authority to other departments and local school sites.

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