Which type of data transfer does NETCONF use?

NETCONF, which stands for Network Configuration Protocol, utilizes XML messages over SSH for data transfer. This design choice provides a robust and secure method for managing network devices. XML is a flexible markup language that allows for structured data representation, making it well-suited for network configurations that can vary widely in format and complexity.

Using SSH (Secure Shell) as the transport layer ensures that the messages are transmitted securely, providing encryption and ensuring the confidentiality and integrity of the data being exchanged. This combination of XML and SSH allows network administrators to perform operations such as configuration management, monitoring, and data retrieval in a secure and standardized way.

In contrast, other options like plain text files or binary data packets do not offer the same level of structure or security, and JSON, while modern and popular for many APIs, is not the primary format used by NETCONF. Therefore, the XML messages over SSH are specifically tailored to meet the requirements of network configuration and management, making this the correct answer.