8.2 Supportability A key component of the customer’s satisfaction with the network, as delivered, is its ability to maintain the high level of performance achieved on the day of delivery throughout the design life of the network. A relatively unsophisticated customer will recognize the poor quality of a design and implementation only when it is frequently out of service; an experienced and knowledgeable customer will examine the design carefully before authorizing implementation and will want to know if it will persistently provide quality performance for its entire life cycle. That customer will also want to know what it takes to operate the design and what it takes to support continued operations. A sophisticated customer will understand the implications of an operations concept and a support concept and will respect the designer’s commitment to ongoing performance after the implementation is complete and the engineers are paid. Supportability is driven by five major factors: (1) the reliability, maintainability, and operational availability (RMA) characteristics of the architecture; (2) workforce, including training and staffing levels; (3) system procedures and technical documentation; (4) tools, both standard and special; and (5) spare and repair parts. Two classes of maintenance need to be performed on the network, once it is deployed: preventive and corrective. Eventually, the maintenance requirements 138 CHAPTER 3 Requirements Analysis: Process are defined as the design is solidified. Requirements for maintenance, during this stage of the system definition, are generally qualitative in nature, such as: • All components will be located where they can be maintained in place with a minimum of disruption to the system as a whole. • Spare parts will be supplied to ensure the replacement of any component whose failure would jeopardize mission performance. RMA The first step in defining RMA requirements is to articulate a representative sample of mission scenarios in which the network is going to be used. These are documented in an anecdotal narrative which describes how the usage will occur, when it will occur, what is necessary for the mission to succeed, and how important it is to the network users. This last item includes how often the network will be used and the level of priority assigned to this mission. For example, the network described in Section 2.5.3 may have users in one building who require access to data in another building which are necessary to pay employees; this data flow path is necessary only from 4 to 5 p.m. on Friday afternoon so that payroll can be accomplished locally over the weekend and employees paid on Monday morning. So this becomes missioncritical during that period and, as a fallback position, may continue as such until the local processing must start or else the payroll will not be accomplished on Monday morning, resulting in disgruntled employees and all the unpleasantness which that can bring on.