Forming equal cost multipath multicast distribution structures

A network device comprising:

• a control unit storing configuration data that specifies an instance number N;
• a multicast protocol executing within the control unit that, based on the instance number N, generates Njoin requests for a plurality of instances N of a multicast group, wherein each of the N instances corresponds to a different multicast distribution structure for the multicast group, and wherein each of the join requests specifies a different one of the N instances of the multicast group to be joined;
• and
• an interface to output the join requests to a plurality of upstream devices located between the network device and a source device for the multicast group to join the multicast group.

A system comprising:

• a source device that provides multicast content for a multicast group;
• and
• a network device coupled to the source device via a plurality of upstream devices located between the network device and the source device,
• wherein the network device sends a join request for each of a specified plurality of instances N for a multicast group from the network device to the plurality of upstream routers,
• wherein each of the N instances corresponds to a different multicast distribution structure for the multicast group, and each of the join requests specifies a different one of the N instances to be joined, and
• wherein the source device selects one of the N instances and sends the multicast content for the multicast group to the network device via the multicast distribution structure corresponding to the selected one of the N instances.