What of the following is NOT an essential characteristic of cloud computing?

C. Third Party Service While third-party services are often associated with cloud computing and can be utilized within cloud environments, they are not considered one of the essential characteristics of cloud computing. The essential characteristics of cloud computing, as defined by the National Institute of Standards and Technology (NIST), include: On-Demand Self-Service: Users can provision and manage cloud resources without requiring interaction with the cloud provider. Broad Network Access: Cloud services are accessible over the network via standard mechanisms. Resource Pooling: Cloud provider's computing resources are pooled to serve multiple users, with different physical and virtual resources dynamically assigned and reassigned. Rapid Elasticity: Computing resources can be rapidly scaled up or down based on demand. Measured Service: Cloud systems automatically control and optimize resource usage, and resource usage can be monitored, controlled, and reported, providing transparency and accountability. Therefore, the correct answer is C. Third Party Service.