Preface Standards development within the Information Technology sector is harmonized with international standards development. Through the CSA Technical Committee on Information Technology (TCIT), Canadians serve as the SCC Mirror Committee (SMC) on ISO/IEC Joint Technical Committee 1 on Information Technology (ISO/IEC JTC1) for the Standards Council of Canada (SCC), the ISO member body for Canada and sponsor of the Canadian National Committee of the IEC. Also, as a member of the International Telecommunication Union (ITU), Canada participates in the International Telegraph and Telephone Consultative Committee (ITU-T). Scope This Recommendation | International Standard specifies the relayed multicast protocol part 2 (RMCP-2), an application-layer protocol that constructs a multicast tree for data delivery from one sender to multiple receivers over an IP-based network, where IP multicast is not fully deployed. RMCP-2 defines relayed multicast data transport capabilities over IP-based networks for simplex group applications. This Recommendation | International Standard specifies the following: a) descriptions of the entities, control and data delivery models of RMCP-2; b) description of the functions and procedures of multicast agents (MAs) to construct a one-to-many relayed data path and to relay data for simplex communication; c) description of the security features of the basic RMCP-2; and d) definitions of messages and parameters of the basic RMCP-2 and secure RMCP-2. Annex A defines a membership authentication procedure for use with the secure RMCP-2. Annex B provides a method for sharing information among session managers (SMs) when multiple SMs are used. Annexes C-G provide informative material related to RMCP-2. Annex H contains an informative bibliography.