Method and apparatus for robust overlay multicast tree management

Provided is a method and apparatus for configuring and managing an overlay multicast data delivery tree in a transmission network having a SM (session manager) and at least one MA (multicast agent). The method includes the steps of at the MA intending to joining a session, obtaining an active neighbor MA list from the SM; detecting information on QoS information of each neighbor MA in the active neighbor MA list, selecting a MA having the most optimized QoS as a parent MA based on the QoS information of each Neighbor MA in the active neighbor MA list, joining an overlay multicast data communication session through the selected parent MA, periodically receiving HB (heart beat) information having information on a path from a root to the MA and determining whether to perform a parent-switching based on me HB information and parent-switching from the current parent MA to a MA having a better QoS when it is determined to perform the parent-switching