What describes the specifications of a data node?

The correct choice accurately defines a data node as a persistent entity that is tasked with storing policy objects and traffic flows. This characteristic means that data nodes maintain the information necessary for enforcing security policies and tracking network communications, which is crucial for effective visibility and control in a network segment.

Data nodes serve as integral parts of Illumio's architecture by handling and retaining necessary information over time, unlike stateless nodes that do not maintain any data between sessions. Their persistent nature allows them to secure and implement policies consistently across the network, ensuring that traffic flows are managed and monitored effectively.

The emphasis on the storage of policy objects indicates the role data nodes play in enforcing security configurations and adapting to changing network conditions. This contrasts sharply with the other options, which either lack the permanence required for effective policy enforcement or inaccurately describe the node's functions in the Illumio system.