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Wireless Networking Handbook
(Publisher: Macmillan Computer Publishing)
Author(s): Jim Geier
ISBN: 156205631x
Publication Date: 09/01/96

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Periodic mobility—often referred to as portability—implies the utilization of network resources from temporary locations, but not necessarily while the user is in transit between locations. Portability implies a temporary connection to the network from a stationary point, but the interface associated with a portable connection should be easy to move, setup, and dismantle. Examples of users requiring portable interfaces include point-of-sale cashiers, conference organizers, and employees working from a temporary office facility. When specifying mobility requirements, be sure to identify the users needing mobility and the range of movement each user or component needs.

Performance Requirements

Performance indicates how well a network provides applications and services. You never hear people complain when performance is too high. Low performance, however, creates disgruntlement because users cannot do their work as quickly as they want or are accustomed. For performance requirements, identify expected values for reliability, availability, and delay, as follows:

  Reliability is the length of time a system or component will operate without disruption. Most product vendors refer to this as Mean Time Before Failure (MTBF).
  Availability defines the period of time the system must be operational. As an example, the availability could indicate that a network should be operational twelve hours a day from 6:00 a.m. until 6:00 p.m.
  Delay is the length of time users or systems can wait for the delivery of a particular service.

Security Requirements

Security requirements identify the information and systems that require protection from particular threats. The degree of security depends on the severity of the consequences the organization would face if the system were damaged or if data were lost. Of course, military and law enforcement agencies require high-level security. Security requirements should address the sensitivity of information processed on the network, the organization’s security regulations, and probability of disasters, such as equipment failure, power failure, viruses, and fire.

System Interface Requirements

Most likely, the system being developed will have to interface and interoperate with existing systems, such as networks and databases. Therefore, system interface requirements describe the architectures of these systems and the hardware, software, and protocols necessary for proper interfacing. If the interfacing method is not known, then you will need to determine a solution during the design phase.

Environmental Requirements

Environmental requirements state conditions, such as weather, pollution, presence and intensity of electromagnetic waves, building construction, and floor space that could affect the operation of the system.

Operational Support Requirements

Operational support requirements define the elements needed to integrate the system into the existing operational support infrastructure. For example, you should require the inclusion of Simple Network Management Protocol (SNMP) if current network monitoring stations require SNMP.

Regulation Requirements

Some organizations might have to conform to certain local, state, or federal regulations; therefore, be certain to specify these conditions as requirements. Regulations imposing safety and environmental procedures place definite requirements on network implementations. The operation of a wireless radio wave adapter, for example, must conform to Federal Communications Commission regulations. Another example is the use of radio-based wireless products on military installations within the United States. The military’s use of these devices is regulated by a special frequency management organization, not the FCC. Therefore, radio-based implementations on military bases must conform to the military’s frequency management policies. In addition, the company itself might have policies and procedures, such as strategic plans and cabling standards, that the implementation should follow.

Budget Requirements

An organization might have a certain amount of money to spend on the system implementation. Budget constraints can affect the choice of solution because some technologies cost more than others to implement. The budget requirements should consider the funding plan for the installation project—the availability of funds at specific times. The reason for this is to best plan the procurement of components and scheduling of resources.

Schedule Requirements

Schedule requirements should include any definite schedule demands that will affect the project. By their nature, organizations impose scheduling conditions on projects, such as availability of project funds, urgency to begin a return on investment, availability of project team members, and interdependency between this project and other projects. Define schedule requirements so the team knows the time frames it can work within. For instance, the design team may have a choice of using a current wireless adapter or waiting eight months for the next, faster release. If the organization must have the system operational within three months, then the team would have to choose the existing product.

Eliciting Information

The objective of eliciting information is to gather as many facts as you can relating to each of the requirements types. This information will enable you to define each of the requirements during a later step. The following is a checklist of items you should consider performing when eliciting requirements:

  Review user needs
  Review existing systems
  Review the environment

The following sections explain each of these steps.

Reviewing User Needs

It’s a good idea to determine what users’ needs are before deploying a system. These needs will lead you to the definition of these types of requirements: user profile and interface, applications, information flow, mobility, performance, security, regulations, budget, and schedule.

The most effective method in reviewing needs of potential users is to interview members of the organization. Who in the organization do you interview? Users and managers. It’s generally not practical to interview every user—just a cross section will do. Talk with managers to obtain a high-level overview of what the people do and how they interact with other organizations. During the interview, ask questions that enable you to define specific requirements. The following sections give samples of good questions and describe the requirements you need to define.


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