Which of the following is NOT a functional area of network management as defined by ISO?

Network management, as defined by the International Organization for Standardization (ISO), encompasses several key functional areas aimed at ensuring the effective operation, maintenance, and security of networks. Among these functional areas, fault management, accounting management, and security management play vital roles in identifying issues, managing resources, and protecting network integrity, respectively.

Fault management focuses on the detection and resolution of network issues, ensuring high availability through timely repairs and maintenance. Accounting management involves the monitoring and reporting of resource usage, facilitating billing and resource allocation. Security management addresses the protection of network resources from unauthorized access, breaches, and other security threats.

Network design, while an important aspect of creating a functional network, is not classified as a management function within the ISO standards. Instead, network design pertains more to the planning and architecture of the network infrastructure itself and how it meets organizational needs. Therefore, this functional area does not align with the operational focus of network management as outlined by ISO, making it the correct choice in this context.