Multicast implementation in a link state protocol controlled ethernet network
View Patent ↗Forwarding state may be installed for sparse multicast trees in a link state protocol controlled Ethernet network by enabling intermediate nodes to install state for one or more physical multicast trees, each of which may have multiple logical multicast trees mapped to it. By mapping multiple logical multicasts to a particular physical multicast, and installing state for the physical multicast, fewer FIB entries are required to implement the multiple multicasts to reduce the amount of forwarding state in forwarding tables at the intermediate nodes. Mapping may be performed by destination nodes before advertising membership in the physical multicast, or may be performed by the intermediate nodes before installing state when a destination node advertises membership in a logical multicast. Intermediate nodes will install state for the physical multicast tree if they are on a shortest path between a source and at least one destination of one of the logical multicasts that has been mapped to the physical multicast.
1. A method of installing forwarding state in a link state protocol controlled Ethernet node of a link state protocol controlled Ethernet network, the method comprising the steps of:
a node of the link state protocol controlled Ethernet network mapping two or more logical multicasts to a physical multicast, the physical multicast including a superset of destinations of the logical multicasts; and
installing forwarding state for the physical multicast in a forwarding information base of the link state protocol controlled Ethernet node, such that traffic of any one of the logical multicasts is forwarded to the superset of destinations.
2. The method of claim 1 , wherein the step of mapping is performed by the link state protocol controlled Ethernet node.
3. The method of claim 1 , wherein the step of mapping is performed by one or more destination nodes on the link state protocol controlled Ethernet network, the method further comprising the steps of receiving link state advertisements containing multicast membership information relating to the physical multicast by the link state protocol controlled Ethernet node and using the multicast membership to perform the step of installing.
4. The method of claim 1 , wherein each of the logical multicasts extends from a common source node, and each of the logical multicasts includes a subset of destination nodes on the link state protocol controlled Ethernet network.
5. The method of claim 4 , wherein at least two of the logical multicasts include different subsets of destination nodes on the link state protocol controlled Ethernet network.
6. The method of claim 5 , wherein the link state protocol controlled Ethernet node installs forwarding state for all destination nodes for which it is on a shortest path between that destination node and the source.
7. The method of claim 1 , wherein the link state protocol controlled Ethernet node forwarding information base contains forwarding state for other physical multicasts, each of the physical multicasts having two or more logical multicasts mapped to them.
8. The method of claim 7 , the method further comprising the steps of identifying packets associated with the physical multicasts, and selectively forwarding the packets according to the forwarding state for the physical multicasts in the forwarding information base.
9. The method of claim 8 , wherein the packets are addressed using logical multicast addresses, the method further comprising the step of mapping the logical multicast addresses to one or more of the physical multicasts before selectively forwarding the packets according to the forwarding state for the physical multicasts.
10. The method of claim 8 , wherein the packets are addressed using the physical multicast address.
11. A method comprising the steps of:
receiving, by a link state protocol controlled Ethernet node, a plurality of link state advertisements containing link state information about a configuration of an Ethernet network;
using the link state advertisements to build a forwarding information base;
receiving, by the link state protocol controlled Ethernet node, a link state advertisement containing multicast membership information related to a logical multicast;
mapping, by the link state protocol controlled Ethernet node, the logical multicast to a physical multicast, the physical multicast including a superset of destinations of two or more logical multicasts mapped to it; and
installing forwarding state in the forwarding information base for the physical multicast, such that traffic of any one of the logical multicasts mapped to the physical multicast is forwarded to the superset of destinations.
12. The method of claim 11 , wherein the step of installing forwarding state is performed only if the link state protocol controlled Ethernet node is on a shortest path between a source of the physical multicast and a destination node associated with the link state advertisement.
13. The method of claim 11 , wherein multiple logical multicasts are able to be mapped to a physical multicast.
14. The method of claim 13 , wherein the step of installing forwarding state is performed only if the link state protocol controlled Ethernet node is on a shortest path between a source of the physical multicast and an advertising node associated with the link state advertisement, and only if the link state protocol controlled Ethernet node has not already installed state between the source and the advertising node for the physical multicast in connection with a second logical multicast.
15. A method of implementing multicast on a link state protocol controlled Ethernet network, the method comprising the steps of:
converting, by a destination node, logical multicast membership information associated with a first logical multicast into physical multicast membership information associated with a physical multicast, wherein the physical multicast subsumes the first logical multicast and at least one other logical multicast and includes a superset of destinations of the subsumed logical multicasts, such that traffic of any one of the plurality of logical multicasts is forwarded to the superset of destinations;
determining by the destination node, whether it has recently advertised membership in the physical multicast;
advertising on the link state protocol controlled Ethernet network, by the destination node, membership to the physical multicast if it has not recently advertised membership in the physical multicast; and
not advertising membership to the physical multicast if it has recently advertised membership in the physical multicast.
16. The method of claim 15 , further comprising the step of receiving, by the destination node, packets associated with each of the subsumed logical multicasts.
17. The method of claim 16 , further comprising the step of discarding, by the destination node, packets for logical multicasts other than the first logical multicast.
18. A link state protocol controlled Ethernet network, comprising:
a source node;
a plurality of destination nodes, the destination nodes being configured to transmit link state advertisements containing link state information about connectivity on the network and multicast membership information; and
a plurality of intermediate nodes, each of the intermediate nodes containing a forwarding information base containing shortest path unicast forwarding route information computed using the link state information between the source and the destination nodes, at least some of the plurality of intermediate nodes including in their forwarding information base multicast forwarding information for a physical multicast derived from the multicast membership information, the physical multicast subsuming a plurality of logical multicasts and including a superset of destinations of the plurality of logical multicasts, such that traffic of any one of the plurality of logical multicasts is forwarded to the superset of destinations.
19. The link state protocol controlled Ethernet network of claim 18 , wherein the plurality of destination nodes are configured to map the logical multicasts to the physical multicast, and wherein the multicast membership information contained in the link state advertisements comprises physical multicast information.
20. The link state protocol controlled Ethernet network of claim 18 , wherein the multicast membership information contained in the link state advertisements comprises logical multicast information, and wherein the intermediate nodes are configured to map the logical multicasts to the physical multicast before installing the forwarding information for the physical multicast into their forwarding information base.
21. The method of claim 1 , wherein the mapping is performed by hashing a multicast ID value with a source MAC address.