Controllable multicast is a multi-level control mechanism that flexibly controls group memberships of hosts. When a user sends a Report message to join a group, the access device analyzes the received Report message and generates a multicast entry only if the requested group is within the group address range configured for controllable multicast.
Traditional multicast services cannot be directly controlled. Users send IGMP/MLD Report messages to join a multicast group so that they can receive multicast packets of the group. Since the emergence of IPTV service, these uncontrollable multicast services can no longer meet carriers' need to make profits. Users are required to pay fees before they can watch programs (join multicast group). If users cannot be authenticated, IPTV service operation cannot be implemented. Controllable multicast was developed to control the rights of users to join multicast groups. This function enables a switch to authenticate requests of users to join multicast groups, and reject invalid and unauthorized requests.