Stateless multicast in multi-domain networks

A method, comprising:

• determining, by a node of a sub-domain of a network domain for a packet of a multicast flow, a set of egress nodes to which the packet is to be delivered;
• determining, by the node from the set of egress nodes to which the packet is to be delivered, a set of external egress nodes that are located outside of the sub-domain and that are served by a common border node of the sub-domain, wherein the common border node of the sub-domain is a common egress point from the sub-domain for the external egress nodes and is a common node in respective shortest paths from the node to the external egress nodes;
• generating, by the node based on the set of external egress nodes, a label switched packet including an encoding of an indication of the set of external egress nodes;
• and
• sending, by the node toward the common border node of the sub-domain based on unicast forwarding, the label switched packet.

An apparatus, comprising:

• at least one processor;
• and
• at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to:
• receive, by a first border node associated with a first sub-domain and based on unicast forwarding, a first label switched packet including an encoding of an indication of a set of external egress nodes for which the first label switched packet is intended, wherein the external egress nodes belong to a multicast group and are disposed outside of the first sub-domain;
• generate, by the first border node based on the first label switched packet, a second label switched packet, wherein the second label switched packet includes an encoding of an indication of a first subset of external egress nodes, from the set of external egress nodes, located within a second sub-domain;
• forward, by the first border node toward a node of the second sub-domain based on multicast forwarding, the second label switched packet;
• generate, by the first border node based on the label switched packet, a third label switched packet, wherein the third label switched packet includes an encoding of an indication of a second subset of external egress nodes, from the set of external egress nodes, located within a third sub-domain;
• and
• forward, by the first border node toward a second border node associated with the second sub-domain and the third sub-domain and based on unicast forwarding, the third label switched packet.