Discovery of forwarders to mitigate asymmetric links in a multicast group

Abstract

Techniques for establishing communications within a multicast group of nodes included in a mesh network include a method comprising: transmitting, by a node included in a mesh network using unicast, a first request to join a multicast group to a multicast group leader of the multicast group; and in response to determining that no message acknowledging the first request has been received from the multicast group leader, broadcasting, by the node, a second request to join the multicast group.

What is claimed is: 
     
         1 . A method, comprising:
 transmitting, by a node included in a mesh network using unicast, a first request to join a multicast group to a multicast group leader of the multicast group; and   in response to determining that no message acknowledging the first request has been received from the multicast group leader, broadcasting, by the node, a second request to join the multicast group.   
     
     
         2 . The method of  claim 1 , further comprising:
 receiving, by the node, a multicast advertisement message from the multicast group leader;   wherein the transmitting of the first request is in response to receiving the multicast advertisement message.   
     
     
         3 . The method of  claim 2 , further comprising:
 adding, by the node, an address of the node to the multicast advertisement message to generate an updated multicast advertisement message; and   transmitting, by the node, the updated multicast advertisement message to one or more neighbor nodes.   
     
     
         4 . The method of  claim 3 , further comprising decrementing, by the node, a hop count limit included in the updated multicast advertisement message. 
     
     
         5 . The method of  claim 2 , wherein:
 the multicast advertisement message includes a first path from the multicast group leader to the node followed by the multicast advertisement message; and   transmitting the first request comprises specifying that the first request is to be transmitted using a second path that is a reverse of the first path.   
     
     
         6 . The method of  claim 5 , wherein:
 the multicast advertisement message further includes a cost of the first path; and   the method further comprises, determining, by the node based on the cost, whether to transmit the first request along the second path.   
     
     
         7 . The method of  claim 1 , further comprising:
 receiving, by the node, a plurality of multicast advertisement messages from the multicast group leader, wherein respective paths taken by respective multicast advertisement messages from the plurality of multicast advertisement messages are recorded in the respective multicast advertisement messages;   determining, by the node based on respective costs of the respective paths, a first path for the first request, the first path being a reverse of a respective path with a lowest respective cost; and   including, by the node, the first path in the first request to specify that the first request is to be transmitted using the first path.   
     
     
         8 . The method of  claim 1 , further comprising:
 receiving, by the node, a first multicast join acknowledgment from the multicast group leader for a second node in the mesh network;   forwarding, by the node, the first multicast join acknowledgement to the second node according to a path included in the first multicast join acknowledgement; and   transmitting, by the node to the multicast group leader, an indication that the node is a multicast forwarder for the multicast group.   
     
     
         9 . The method of  claim 1 , wherein the second request is forwardable by one or more additional nodes in the mesh network subject to a maximum hop limit. 
     
     
         10 . The method of  claim 9 , further comprising;
 receiving, by the node, a third request from a second node in the mesh network to join the multicast group; and   forwarding, by the node, the third request to the multicast group leader according to a path included in the third request.   
     
     
         11 . One or more non-transitory computer readable media storing instructions that, when executed by one or more processors of a first networking device in a mesh network, cause the one or more processors to perform operations comprising:
 sending a unicast message to a leader networking device of a multicast group, the unicast message including a first join request for the multicast group; and   in response to determining that an acknowledgment to the first join request has not been received from the leader networking device, broadcasting a broadcast message to the leader networking device, the broadcast message including a second join request for the multicast group.   
     
     
         12 . The one or more non-transitory computer readable media of  claim 11 , wherein the operations further comprise:
 receiving an advertisement message for the multicast group initiated by the leader networking device; and   sending the unicast message in response to receiving the advertisement message.   
     
     
         13 . The one or more non-transitory computer readable media of  claim 12 , wherein the operations further comprise:
 recording an address of the first networking device in an address vector included in the advertisement message; and   sending, to one or more networking devices that are neighbors to the first networking device, the advertisement message with the recorded address of the first networking device.   
     
     
         14 . The one or more non-transitory computer readable media of  claim 12 , wherein:
 the advertisement message includes a first address vector recording addresses of networking devices along a route followed by the advertisement message from the leader networking device to the first networking device; and   the operations further comprise including a second address vector in the unicast message to specify a route for the unicast message, the second address vector being a reverse of the first address vector.   
     
     
         15 . The one or more non-transitory computer readable media of  claim 11 , wherein the operations further comprise:
 receiving a multicast join acknowledgment for a second networking device in the mesh network, the multicast join acknowledgement including an address vector specifying a route for the multicast join acknowledgement;   forwarding the multicast join acknowledgement to a next networking device in the address vector; and   sending to the leader networking device, a message indicating that the first network device is a multicast forwarding device for the multicast group for a specified duration.   
     
     
         16 . The one or more non-transitory computer readable media of  claim 11 , wherein the operations further comprise:
 receiving a second unicast message, the second unicast message including a third join request for the multicast group made by a second networking device and an address vector specifying a route for the second unicast message; and   sending the second unicast message to a next networking device included in the address vector.   
     
     
         17 . A node device in a mesh network, the node device comprising:
 one or more processors; and   a memory storing instructions that, when executed by the one or more processors, cause the one or more processors to perform operations comprising:
 in response to receiving an advertisement for a multicast group from a leader device of a multicast group, transmitting, via unicast to the leader device, a first multicast join message for the multicast group; and 
 in response to determining that a multicast join acknowledgment message has not been received from the leader device, broadcasting a second multicast join message to the leader device. 
   
     
     
         18 . The node device of  claim 17 , wherein the operations further comprise:
 adding an address of the node device to an ordered list of addresses included in the advertisement, the ordered list of addresses indicating a path followed by the advertisement through the mesh network; and   transmitting, to one or more neighboring devices of the node device, the advertisement with the address of the node device.   
     
     
         19 . The node device of  claim 17 , wherein:
 the advertisement includes a first ordered list of addresses indicating a path followed by the advertisement through the mesh network; and   the operations further comprise:
 reversing the first ordered list of addresses to generate a second ordered list of addresses; and 
 including the second ordered list of addresses in the first multicast join message to indicate a path for the first multicast join request to follow through the mesh network. 
   
     
     
         20 . The node device of  claim 17 , wherein the operations further comprise:
 receiving a multicast join acknowledgment message for a second node device in the mesh network, the multicast join acknowledgement message including an ordered list of addresses indicating a path through the mesh network to be followed by the multicast join acknowledgement message;   transmitting the multicast join acknowledgement message to a next node device in the ordered list of addresses; and   transmitting to the leader device, a message declaring that the node device is acting as a multicast forwarder for the multicast group for a declared duration.