If an existing network is part of this project, monitoring this network, as well as other parts of the system and its environment, can provide valuable information about the current behavior of users, applications, and devices and their requirements for the new network. Monitoring can also validate your and your customer’s definitions of the problems with the existing network. When it is possible to monitor the network, you will need to determine what data you want to collect (based on what you want to accomplish with the data), any strategic places in the network where you want to collect this data, and the frequency and duration of data collection. At this point in the process you should have several sets of information with which you can begin your network analysis. You may have historical data from network management; data captured during monitoring; requirements gathered from users, staff, and management; the customer’s definition of the problem; and your definition. All of these data are used in the network analysis, of which there are three parts: requirements or needs analysis, flow analysis, and a risk (security) analysis. Information in these analyses can be placed on the customer’s internal Web page, as mentioned earlier, although some information (e.g., the results of the risk analysis) may have to be kept private. Results of the network analysis are used in the architecture and design processes, where sets of options are developed, including potential architectures, designs, topologies, technologies, hardware, software, protocols, and services. These sets of options are then evaluated to determine the optimal solutions for the problems. Criteria need to be developed throughout the analysis, architecture, and design processes in order to evaluate these options. Along with these criteria, you will use the results of the network analysis, including requirements, tradeoffs, and dependencies between options. A Systems Methodology 27 Having selected one or more options, you can complete the network architecture and design and prepare for implementation. At this point you may consider developing a project plan to determine schedule, budget, and resources, as well as major and minor milestones, checkpoints, and reviews. 1.5 A Systems Methodology We begin the network analysis process with a discussion of the systems methodology approach to networking. Applying a systems methodology to network analysis, architecture, and design is a relatively new approach, particularly in the Internet Protocol (IP) world. Systems methodology (as applied to networking) means viewing the network that you are architecting and designing, along with a subset of its environment (everything that the network interacts with or impacts), as a system. Associated with this system are sets of services (levels of performance and function) that are offered by the network to the rest of the system.