This Recommendation | International Standard describes a protocol for N-plex multicast transport over Internet where IP multicast is supported. It provides the mechanisms of session control and error control. For session control, one participant is designated to manage creation/termination of a connection; join/leave of a participant; and tokens which allow the specific participants to send data. For error control, it provides the mechanisms of tree-based loss recovery; control tree construction with two-layer logical tree; and logical tree adaptation with packet delivery status. This Specification describes the protocol details such as packet format, procedures and parameter values. This protocol can be used for the applications which require many-to-many reliable data delivery service.