This Recommendation | International Standard describes an application-layer protocol which constructs multicast tree for data delivery from a sender to multiple receivers over Internet where IP multicast is not fully deployed. The specified relayed multicast protocol consists of multicast agent and session manager. This Recommendation | International Standard specifies a series of functions and procedures of multicast agent to construct one-to-many relayed data path and to relay simplex data. It also specifies the operations of session manager to manage multicast sessions. This protocol can be used for applications that require one-to-many data delivery services, such as multimedia streaming service, file dissemination service, etc.

Amendment 1 describes the security functionalities of an application-level relayed multicast protocol for one-to-many group applications. The protocol provides various security facilities to fulfil general as well as specific security requirements. Some detailed functions that can operate with a variety of standardized security mechanisms are provided. This amendment enforces the existing RMCP protocol security.

Amendment 2 revises messages and code values.