Kyungpook National University This document is a part of the ITU-T Recommendation and ISO/IEC International Standard, named the Enhanced Communications Transport Protocol (ECTP), which is a multicast transport protocol designed to support Internet multicast applications. This third part of ECTP (ECTP-3) describes the protocol specification for the duplex multicast transport. In a duplex connection, a single multicast sender, named TC-Owner (TO), transmits multicast data to the other group members, while some of the participating TS-users may send unicast data to the TO over the reverse data channel.