Multicast implementation in a link state protocol controlled ethernet network
Forwarding state is 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. 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 operating an Ethernet bridge, the method comprising:
exchanging link state information with peer bridges, wherein the link state information comprises community of interest identifiers associated with peer bridges;
determining shortest paths between peer bridges based on the exchanged link state information using a shortest path algorithm;
populating at least one forwarding information base (FIB) with multicast MAC addresses in association with egress ports determined using the shortest paths and the community of interest identifiers associated with peer bridges, each multicast MAC address corresponding to a respective peer bridge and a respective community of interest, the peer bridge being a root of a respective multicast tree for the community of interest; and
forwarding multicast packets based on their respective multicast MAC addresses according to the forwarding information base (FIB) such that multicast connectivity for each community of interest is confined to that community of interest.
2. The method of claim 1 , wherein the shortest path algorithm is operable, when multiple equal cost shortest paths are available between two bridges, to select one of the equal cost shortest paths between the two bridges consistent with path selections at peer bridges.
3. The method of claim 1 , further comprising discarding the incoming multicast packet when there is no entry in the at least one FIB for the multicast MAC address of the incoming packet.
4. The method of claim 1 , further comprising performing a reverse path forwarding check to determine whether the incoming multicast packet arrives on a port which does not match an egress port associated in the at least one FIB with a unicast source MAC address of the incoming packet.
5. The method of claim 1 , further comprising discarding an incoming multicast packet when the incoming multicast packet arrives on an ingress port which does not match a port associated in the at least one FIB with the multicast MAC address of the incoming packet.
6. The method of claim 1 , further comprising determining at least one multicast tree based on the exchanged link state information before populating the forwarding information base with multicast MAC addresses.
7. The method of claim 1 , wherein the community of interest identifiers are I-SIDs.
8. The method of claim 1 , wherein:
the exchanged link state information further comprises a source attribute for each node and each community of interest supported by that node, the source attribute indicating whether that node is to act as a source node for that community of interest;
the exchanged link state information further comprises a sink attribute for each node and each community of interest supported by that node, the sink attribute indicating whether that node is to act as a sink node for that community of interest; and
populating the at least one forwarding information base with multicast MAC addresses comprises populating the at least one forwarding information base with multicast MAC addresses corresponding to respective peer bridges and respective communities of interest to be consistent with the source and sink attributes of each node for the communities of interest corresponding to the multicast MAC addresses.
9. The method of claim 1 , wherein:
exchanging link state information with peer bridges comprises exchanging link state information comprising unicast MAC address supported by each peer bridge; and
populating the at least one forwarding information base comprises populating the forwarding information base with unicast MAC addresses supported by peer bridges using the determined shortest paths;
the method further comprising forwarding incoming packets with unicast MAC addresses using the forwarding information base.
10. The method of claim 9 , further comprising:
performing a reverse path forwarding check for incoming packets with unicast MAC addresses, the reverse path forwarding check being considered a failure when an incoming packet arrives on an ingress port which does not match an egress port associate in the forwarding information base with a source MAC address of the incoming packet; and
discarding incoming packets for which the reverse path forwarding check is considered a failure.
11. A method of operating an Ethernet network comprising a plurality of Ethernet bridges, the method comprising operating at least one of the bridges according to the method defined by claim 1 .
12. The method of claim 11 , comprising operating each bridge of the network according to the method comprising:
exchanging link state information with peer bridges, wherein the link state information comprises community of interest identifiers associated with peer bridges;
determining shortest paths between peer bridges based on the exchanged link state information using a shortest path algorithm;
populating at least one forwarding information base (FIB) with multicast MAC addresses in association with egress ports determined using the shortest paths and the community of interest identifiers associated with peer bridges, each multicast MAC address corresponding to a respective peer bridge and a respective community of interest, the peer bridge being a root of a respective multicast tree for the community of interest; and
forwarding multicast packets based on their respective multicast MAC addresses according to the forwarding information base (FIB) such that multicast. connectivity for each community of interest is confined to that community of interest.
13. An Ethernet bridge, comprising:
a routing module operable:
to exchange link state information with peer bridges, wherein the link state information comprises community of interest identifiers associated with peer bridges; and
to determine shortest paths between peer bridges based on the exchanged link state information using a shortest path algorithm;
at least one forwarding information base (FIB) populated with multicast MAC addresses in association with egress ports determined using the shortest paths and the community of interest identifiers associated with peer bridges, each multicast MAC address corresponding to a respective peer bridge and a respective community of interest, the peer bridge being a root of a respective multicast tree for the community of interest; and
a forwarding module operable to forward multicast packets based on their respective multicast MAC addresses according to the forwarding information base (FIB) such that multicast connectivity for each community of interest is confined to that community of interest.
14. The bridge of claim 13 , wherein the shortest path algorithm is operable, when multiple equal cost shortest paths are available between two bridges, to select one of the equal cost shortest paths between the two bridges consistent with path selections at peer bridges.
15. The bridge of claim 13 , wherein the forwarding module is further operable to discard the, incoming multicast packet when there is no entry in the at least one FIB for the multicast MAC address of the incoming packet.
16. The bridge of claim 13 , wherein the forwarding module is further operable to perform a reverse path forwarding check to determine whether the incoming multicast packet arrives on a port which does not match an egress port associated in the at least one FIB with a unicast source
17. The bridge of claim 13 , wherein the forwarding module is further operable to discard an incoming multicast packet when the incoming multicast packet arrives on an ingress port which does not match a port associated in the at least one FIB with the multicast MAC address of the incoming packet.
18. The bridge of claim 13 , wherein the routing module is further operable to determine at least one multicast tree based on the exchanged link state information before populating the forwarding information base with multicast MAC addresses.
19. The bridge of claim 13 , wherein the community of interest identifiers are I-SIDs.
20. The bridge of claim 13 , wherein:
the routing module is operable to the exchange link state information further comprising a source attribute for each node and each community of interest supported by that node, the source attribute indicating whether that node is to act as a source node for that community of interest;
the routing module is operable to exchange link state information further comprising a sink attribute for each node and each community of interest supported by that node, the sink attribute indicating whether that node is to act as a sink node for that community of interest; and
the at least one forwarding information base is populated with multicast MAC addresses corresponding to respective peer bridges and respective communities of interest to be consistent with the source and sink attributes of each node for the communities of interest corresponding to the multicast MAC addresses.
21. The bridge of claim 13 , wherein:
the routing module is operable to exchange link state information further comprising unicast MAC address supported by each peer bridge; and
the at least one forwarding information base is further populated with unicast MAC addresses supported by peer bridges using the determined shortest paths; and
the forwarding module is further operable to forward incoming packets with unicast MAC addresses using the forwarding information base.
22. The bridge of claim 21 , wherein the forwarding module is further operable:
to perform a reverse path forwarding check for incoming packets with unicast MAC addresses, the reverse path forwarding check being considered a failure when an incoming packet arrives on an ingress port which does not match an egress port associate in the forwarding information base with a source MAC address of the incoming packet; and
to discard incoming packets for which the reverse path forwarding check is considered a failure.
23. An Ethernet network comprising a plurality of Ethernet bridges, at least one of the bridges being a bridge as defined by claim 13 .
24. The network of claim 23 , wherein each bridge of the network is a bridge comprising:
a routing module operable:
to exchange link state information with peer bridges, wherein the link state information comprises community of interest identifiers associated with peer bridges; and
to determine shortest paths between peer bridges based on the exchanged link state information using a shortest path algorithm;
at least one forwarding information base (FIB) populated with multicast MAC addresses in association with egress ports determined using the shortest paths and the community of interest identifiers associated with peer bridges, each multicast MAC address corresponding to a respective peer bridge and a respective community of interest, the peer bridge being a root of a respective multicast tree for the community of interest; and
a forwarding module operable to forward multicast packets based on their respective multicast MAC addresses according to the forwarding information base (FIB) such that multicast connectivity for each community of interest is confined to that community of interest.