Ravindranath, R., Reddy, T., and G. Salgueiro, "Session Traversal Utilities for NAT (STUN) Message Handling for SIP Back-to-Back User Agents (B2BUAs)", RFC 7584, DOI 10.17487/RFC7584, July 2015, <https://www.rfc-editor.org/info/rfc7584>.