The US National Institute of Standards and Technology (NIST) and its National Cybersecurity Center of Excellence (NCCoE) issue for public comments draft NISTIR 8349 -a methodology for characterizing network behavior of IoT devices. The report describes an approach to capturing and documenting the network communication behavior of IoT devices. Manufacturers, network administrators, and others can use the techniques and tools described in the report to capture network communications from IoT devices, analyze network captures, and generate MUD files to help ensure IoT devices perform as intended. The report also describes the current state of implementing the approach and proposals for future development.