Multicast routing over unidirectional links

A system comprising:

• a first network device;
• a second network device;
• a unidirectional link coupling the first network device to the second network device;
• and
• a bidirectional path coupling the first network device to the second network device, wherein
• the second network device is configured to:
• receive a multicast protocol control message sent from the first network device via the unidirectional link;
• extract a unicast destination address from the multicast protocol control message received via the unidirectional link;
• and
• send a reply message;
• a destination address of the reply message is the unicast destination address extracted from the multicast protocol control message, and
• the reply message is sent to the first network device via the bidirectional path.

A network device comprising:

• a send-only interface configured to be coupled to a unidirectional link;
• a multicast RPF routing table entry corresponding to the send-only interface, wherein
• the multicast RPF routing table entry comprises a first metric, and
• the first metric identifies an infinite efficiency associated with a route comprising the unidirectional link;
• and
• a unicast routing table entry corresponding to the send-only interface, wherein
• the unicast routing table entry comprises a second metric, and
• the second metric identifies that a finite efficiency is associated with the route comprising the unidirectional link.

A network device comprising:

• a receive-only interface configured to receive messages from a unidirectional link;
• a bidirectional interface configured to send and receive messages on a bidirectional link;
• and
• a routing module coupled to the receive-only interface and to the bidirectional interface, wherein
• the routing module is configured to extract a unicast destination address from a first multicast protocol control message received via the receive-only interface,
• the routing module is configured to send a second multicast protocol control message from the bidirectional interface, and
• a destination address of the second multicast protocol control message is the unicast destination address extracted from the first multicast protocol control message.

A system comprising:

• means for maintaining a multicast adjacency state, wherein
• the multicast adjacency state is associated with an interface coupled to receive messages from a network device via a unidirectional link, wherein
• the multicast adjacency state identifies a network address of the network device;
• and
• means for sending a multicast protocol control message to the network device via a bidirectional path, wherein
• a destination address of the network multicast protocol control message is the network address in the multicast adjacency state.