Optimizing IP multicast delivery with use of local source nodes and the propagation of advertisements therefor

1. A method comprising:

at a network node configured to connect in a network fabric of interconnected network nodes,

identifying that the network node is established as part of a multicast distribution tree of nodes that forward Internet Protocol (IP) multicast traffic originating from a source node to one or more host receiver devices of a multicast group, the IP multicast traffic comprising multicast data packets originating from the source node; and

in response to the identifying, propagating to one or more adjacent network nodes in the network fabric a message for advertising the network node as a candidate local source node at which to join the multicast group to receive via the network node the IP multicast traffic originating from the source node.

2. The method of claim 1 , wherein propagating the message is part of a flooding of messages in the network fabric for advertising a plurality of network nodes of the multicast distribution tree as candidate local source nodes for joining the multicast group.

3. The method of claim 2 , wherein the flooding of messages is compatible with Protocol Independent Multicast (PIM) flooding mechanism (PFM) and source discovery (SD) according to Request for Comments (RFC) 8364.

4. The method of claim 2 , wherein the flooding of messages is performed with use of an Interior Gateway Protocol (IGP) extension.

5. The method of claim 1 , further comprising:

at the network node,

after the propagating of the message for advertising, receiving from an adjacent network node a join request for joining a host receiver device to the multicast group; and

joining the host receiver device in the multicast group at the network node, for the host receiver device to receive the IP multicast traffic originating from the source node via the network node.

6. The method of claim 5 , wherein the join request comprises a Protocol Independent Multicast (PIM) join message including a PIM reverse path forwarding (RPF) vector which specifies an IP address of an edge router to the host receiver device.

7. The method of claim 1 , wherein the message for advertising the network node as the candidate local source node includes a multicast source address associated with the source node, a multicast group address associated with the multicast group, and a loopback address associated with the network node.

8. The method of claim 1 , wherein the message for advertising the network node as the candidate local source node includes a reachability metric comprising a number of hops to the network node.

9. The method of claim 1 , wherein the message for advertising the network node as the candidate local source node includes a scope value to limit propagation of the message.

10. The method of claim 1 , further comprising:

identifying whether a distance between the network node and another network node which serves as the source node or candidate local source node in the multicast distribution tree is greater than a threshold value; and

wherein propagating the message for advertising is performed based on identifying that the distance is greater than the threshold value.

11. The method of claim 1 , further comprising:

identifying whether a distance between the network node and another network node which serves as an edge node in the network fabric is less than a threshold value; and

wherein propagating the message for advertising is performed based on identifying that the distance is less than the threshold value.

12. The method of claim 1 , further comprising:

identifying whether a number of candidate host receivers to receive the IP multicast traffic is greater than a threshold value; and

wherein propagating the message for advertising is performed based on identifying that the number is greater than the threshold value.

13. The method of claim 1 , further comprising:

identifying whether a number of candidate host receivers to receive the IP multicast traffic is greater than a first threshold value;

if the number of candidate host receivers is greater than the first threshold value, performing a trickle operation which includes:

delaying for a random time period;

identifying whether a number of received network node advertisements received over the random time period is greater than a second threshold value; and

if the number of received network node advertisements is greater than the second threshold value, electing to serve as the candidate local source node and performing the propagating of the message.

14. A network node comprising:

one or more processors;

a plurality of interfaces configured to connect in a network fabric of a plurality of network nodes;

the one or more processors being configured to:

identify that the network node is established as part of a multicast distribution tree of nodes that forward Internet Protocol (IP) multicast traffic originating from a source node to one or more host receiver devices of a multicast group, the IP multicast traffic comprising multicast data packets originating from the source node;

in response to the identifying, propagating to one or more adjacent network nodes a message for advertising the network node as a candidate local source node at which to join the multicast group to receive via the network node the IP multicast traffic originating from the source node; and

after the propagating of the message, receive from an adjacent network node a join request for joining a host receiver device to the multicast group and, in response, join the host receiver device in the multicast group at the network node for the host receiver device to receive via the network node the IP multicast traffic originating from the source node.

15. A method comprising:

at an edge router configured to connect in a network fabric of interconnected network nodes,

receiving a message which advertises a network node as a candidate local source node at which to join a multicast group to receive, via the network node, Internet Protocol (IP) multicast traffic originating from a source node, the network node being established as part of a multicast distribution tree of nodes that forward the IP multicast traffic which comprises multicast data packets originating from the source node to one or more host receiver devices of the multicast group;

storing data associated with the message for advertising the network node as the candidate local source node, the data including a reachability metric associated with the candidate local source node;

receiving from a host receiver device a join request for joining a host receiver device to the multicast group;

selecting one of the source node or the candidate local source node based at least on the reachability metric associated with the candidate local source node; and

causing the host receiver device to be joined in the multicast group at the selected one of the source node or the candidate local source node for the host receiver device to receive the IP multicast traffic of the multicast group.

16. The method of claim 15 , wherein the message which advertises the network node as the candidate local source node includes a multicast source address associated with the source node, a multicast group address associated with the multicast group, and a loopback address associated with the network node.

17. The method of claim 15 , wherein the reachability metric associated with the candidate local source node comprises a number of hops to reach the candidate local source node.

18. The method of claim 15 , further comprising:

comparing a reachability metric associated with the source node and the reachability metric associated with the candidate local source node,

wherein the selecting is performed based on the comparing.

19. The method of claim 15 ,

wherein the join request comprises a PIM join message which includes a PIM reverse path forwarding (RPF) vector that specifies an IP address of an edge router to the host receiver device.

20. The method of claim 15 , further comprising:

wherein a message for advertising is received from each one of a plurality of network nodes established as part of the multicast distribution tree, and wherein data associated with each message from each network node is stored, where the data for each message includes a reachability metric associated with the network node; and

selecting one of the plurality of network nodes as a local source node for receiving the IP multicast traffic based on the reachability metric associated with each network node.