Method and apparatus for shortest path bridging of multicast traffic

1. A method for determining shortest path bridging (SPB) of multicast frames within a communications network, comprising:

at each of a plurality of nodes within the network supporting a first subset of service instances, determining a designated node (DN) according to a commonly agreed mechanism associated with the first subset of service instances, said commonly agreed mechanism configured to determine a single DN from within said plurality of nodes within the network supporting said first subset of service instances;

at each of the plurality of nodes, determining a shortest path between the DN and each of the plurality of nodes; and

at each of the plurality of nodes, selecting for inclusion in a respective forwarding tree for multicast only those determined shortest paths from the DN traversing the respective node.

2. The method of claim 1 , wherein the respective forwarding tree for multicast comprises a *,G tree.

3. The method of claim 1 , wherein the selecting comprises pruning a forwarding tree including the shortest paths between the DN and each of the plurality of nodes.

4. The method of claim 1 , further comprising:

at each of the plurality of nodes, determining a shortest path between the respective node and the remaining nodes of interest.

5. The method of claim 4 , wherein the respective forwarding tree for multicast comprises a *,G tree.

6. The method of claim 1 , wherein the commonly agreed mechanism comprises a system identification field.

7. The method of claim 1 , wherein the commonly agreed mechanism comprises a bridge priority field.

8. The method of claim 1 , wherein the commonly agreed mechanism comprises any existing type length value (TLV) associated with a shortest path bridging protocol.

9. The method of claim 1 , wherein the commonly agreed mechanism comprises a new type length value (TLV) introduced to the shortest path bridging protocol.

10. The method of claim 1 , wherein the communications network supports additional service instance subsets, the method being repeated for each of the additional service instance subsets using a corresponding plurality of supporting nodes.

11. The method of claim 10 , wherein each service instance subset uses a respective commonly agreed mechanism.

12. The method of claim 10 , wherein a PBB multicast is encoded using a structure comprising a first field including an Organizationally Unique Identifier (OUI), and a second field including 24 bits of PBB service identifier I-SID.

13. The method of claim 12 , wherein the encoded PBB multicast is used for shortest path bridging (SPB) of PBB multicast.

14. The method of claim 13 , wherein the encoded PBB multicast replaces a source specific multicast structure which uses a unique source identifier plus 24 bit I-SID.

15. The method of claim 1 , wherein said single DN determined at each of said plurality of nodes comprises a first DN within a sequence of potential DNs.

16. The method of claim 15 , wherein a second DN within the sequence of potential DNs determined at each of said plurality of nodes comprises a backup DN.

17. The method of claim 1 , further comprising:

at each of said plurality of nodes within the network supporting said first subset of service instances, in response to the determined DN being unable to perform the DN function, selecting as the DN a next potential DN within said sequence of potential DNs.

18. A tangible and non-transient computer readable storage medium storing instructions which, when executed by a computer, configure the operation of the computer to provide a method for determining shortest path bridging (SPB) of multicast frames within a communications network, the method comprising:

at each of a plurality of nodes within the network supporting a first subset of service instances, determining a designated node (DN) according to a commonly agreed mechanism associated with the first subset of service instances, said commonly agreed mechanism configured to determine a single DN from within said plurality of nodes within the network supporting said first subset of service instances;

at each of the plurality of nodes, determining a shortest path between the DN and each of the plurality of nodes; and

at each of the plurality of nodes, selecting for inclusion in a respective forwarding tree for multicast only those determined shortest paths from the DN traversing the respective node.

19. The computer readable storage medium of claim 18 , wherein said single DN determined at each of said plurality of nodes comprises a first DN within a sequence of potential DNs.

20. A computer program product wherein non-transitory computer instructions executed by a processor in a telecom network element configure the operation of the telecom network element to provide a method for determining shortest path bridging (SPB) of multicast frames within a communications network, the method comprising:

at each of a plurality of nodes within the network supporting a first subset of service instances, determining a designated node (DN) according to a commonly agreed mechanism associated with the first subset of service instances, said commonly agreed mechanism configured to determine a single DN from within said plurality of nodes within the network supporting said first subset of service instances;

at each of the plurality of nodes, determining a shortest path between the DN and each of the plurality of nodes; and at each of the plurality of nodes, selecting for inclusion in a respective forwarding tree for multicast only those determined shortest paths from the DN traversing the respective node.

21. The computer program product of claim 20 , wherein said single DN determined at each of said plurality of nodes comprises a first DN within a sequence of potential DNs.