Recommendation ITU-T X.603 describes the relayed multicast protocol part 3 (RMCP-3) which is an application-layer relayed multicast protocol that operates over the IP-based network where the IP multicast is not fully deployed. The RMCP-3 constructs a relayed multicast tree for delivering user data from multiple senders to multiple receivers. The relayed multicast tree consists of multicast agent and session manager. The multicast agent relays many‑to-many multicast data along the relayed multicast tree, whereas the session manager manages the RMCP-3 session. This Recommendation specifies the functions and the procedures of the multicast agent and session manager. The RMCP-3 can support applications requiring capability of many-to-many multicast data delivery. Examples of such applications are multimedia conference, panel discussion, and network gaming.