(My apologies for doing the review late.) I have reviewed this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG. These comments were written primarily for the benefit of the security area directors. Document editors and WG chairs should treat these comments just like any other last call comments. This document discusses point to point and multi-endpoint topologies used in Real-time Transport Protocol (RTP)-based environments. In particular, centralized topologies commonly employed in the video conferencing industry are mapped to the RTP terminology. This document is updated with additional topologies and replaces RFC 5117. Summary The document is well written and has lots of useful security related details. I have very passing familiarity with RTP/RTCP, but the Security Considerations looks reasonable to me.