Department of Computer Science and Engineering Department of Electrical and Computer Engineering Huawei Huawei Fraunhofer Institute for Secure Information Technology This document proposes an information model and the corresponding YANG data model of an interface for monitoring Network Security Functions (NSFs) in the Interface to Network Security Functions (I2NSF) framework. If the monitoring of NSFs is performed with the NSF monitoring interface in a standard way, it is possible to detect the indication of malicious activity, anomalous behavior, the potential sign of denial-of-service attacks, or system overload in a timely manner. This monitoring functionality is based on the monitoring information that is generated by NSFs. Thus, this document describes not only an information model for the NSF monitoring interface along with a YANG tree diagram, but also the corresponding YANG data model.