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 operating an Ethernet bridge, comprising:
exchanging link state information with peer bridges, wherein the link state information comprises MAC addresses associated with peer bridges;
determining shortest paths between bridges based on the exchanged link state information using a shortest path algorithm which 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 such that connectivity between the two bridges follows the same path in both directions;
populating a forwarding information base (FIB) with egress ports and MAC addresses associated with peer bridges using the determined shortest paths;
performing a reverse path forwarding check (RPFC) for an incoming packet, the RPFC being considered a failure when the incoming packet arrives on a port which does not match an egress port associated in the FIB with a source MAC address of the incoming packet; and
discarding the incoming packet when the RPFC of the incoming packet is considered a failure.
2. A method as defined in claim 1 , the method further comprising forwarding the incoming packet when the RPFC is not considered a failure.
3. A method as defined in claim 2 , wherein the step of forwarding the incoming packet comprises forwarding the incoming packet via an egress port associated in the FIB with a destination MAC address of the incoming packet.
4. A method as defined in claim 1 , wherein the MAC addresses associated with peer bridges comprise at least one unicast MAC address.
5. A method as defined in claim 4 , wherein the at least one unicast MAC address is assigned to one of a line card, a virtual switch instance (VSI) or UNI port or other arbitrary naming of terminations at a bridge, or is representative of a MAC termination behind the bridge.
6. A method as defined in claim 1 , wherein the link state information comprises at least one service identifier.
7. A method as defined in claim 6 , wherein the link state information comprises at least one extended service identifier (I-SID).
8. A method as defined in 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 such that go and return unicast paths are co-routed.
9. A method as defined in 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 such that go multicast and return unicast paths are co-routed.
10. A method as defined in claim 1 , wherein the Ethernet bridge participates in multiple VLANs, each VLAN having an associated VLAN identifier and wherein:
the step of exchanging link state information with peer bridges, comprises exchanging VLAN identifiers;
the step of determining shortest paths between bridges comprises using a shortest path algorithm which is operable, when multiple equal cost shortest paths are available between two bridges, to select, for each VLAN, one of the equal cost shortest paths between the two bridges consistent with path selections at peer bridges for that VLAN such that connectivity between the two bridges follows the same path in both directions;
the step of populating a forwarding information base (FIB) comprises populating the FIB with egress ports, VLAN identifiers and MAC addresses associated with peer bridges using the shortest paths determined for the VLANs; and
the step of performing a reverse path forwarding check (RPFC) for the incoming packet comprises considering the RPFC to be a failure when the incoming packet arrives on a port which does not match an egress port associated in the FIB with a VLAN identifier and the source MAC address of the incoming packet.
11. A method as defined in claim 10 , wherein the step of determining shortest paths between bridges comprises operating the shortest path algorithm according to a first ranking algorithm for a first VLAN and according to a second ranking algorithm for a second VLAN.
12. A method as defined in claim 1 , further comprising temporarily disabling the RPFC for unicast traffic when the link state information changes.
13. A method as defined in claim 1 , wherein the shortest path algorithm employs symmetric link metrics.
14. A method as defined in claim 1 , wherein the step of populating a forwarding information base (FIB) comprises populating the FIB with egress ports and MAC addresses associated with a peer bridge only for selected shortest paths between the peer bridge and other bridges, each selected path including the bridge and being between the peer bridge and a bridge that is in at least one community of interest with the peer bridge.
15. A method as defined in claim 1 , wherein the MAC addresses associated with peer bridges comprise at least one multicast MAC address.
16. An Ethernet bridge, comprising:
a routing element operable:
to exchange link state information with peer bridges, wherein the link state information comprises MAC addresses associated with peer bridges; and
to determine shortest paths between bridges based on the exchanged link state information using a shortest path algorithm which 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 such that connectivity between the two bridges follows the same path in both directions;
a forwarding information base (FIB) populated with egress ports and MAC addresses associated with peer bridges using the determined shortest paths; and
a forwarding element operable:
to perform a reverse path forwarding check (RPFC) for an incoming packet, the RPFC being considered a failure when the incoming packet arrives on a port which does not match an egress port associated in the FIB with a source MAC address of the incoming packet; and
to discard the incoming packet when the RPFC of the incoming packet is considered a failure.
17. An Ethernet bridge as defined in claim 16 , wherein the forwarding element is operable to forward the incoming packet when the RPFC is not considered a success.
18. An Ethernet bridge as defined in claim 17 , wherein the forwarding element is operable to forward the incoming packet via an egress port associated in the FIB with a destination MAC address of the incoming packet.
19. An Ethernet bridge as defined in claim 16 , wherein the MAC addresses associated with peer bridges comprise at least one unicast MAC address.
20. An Ethernet bridge as defined in claim 19 , wherein the at least one unicast MAC address is assigned to one of a line card, a virtual switch instance (VSI) or UNI port or other arbitrary naming of terminations at a bridge, or is representative of a MAC termination behind the bridge.
21. An Ethernet bridge as defined in claim 16 , wherein the link state information comprises at least one service identifier.
22. An Ethernet bridge as defined in claim 21 , wherein the link state information comprises at least one extended service identifier (I-SID).
23. An Ethernet bridge as defined in claim 16 , 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 such that go and return unicast paths are co-routed.
24. An Ethernet bridge as defined in claim 16 , 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 such that go multicast and return unicast paths are co-routed.
25. An Ethernet bridge as defined in claim 16 , operable to participate in multiple VLANs, each VLAN having an associated VLAN identifier, wherein:
the routing element is operable to exchange link state information comprising VLAN identifiers with peer bridges;
the shortest path algorithm is operable, when multiple equal cost shortest paths are available between two bridges, to select, for each VLAN, one of the equal cost shortest paths between the two bridges consistent with path selections at peer bridges for that VLAN such that connectivity between the two bridges follows the same path in both directions;
the FIB is populated with egress ports, VLAN identifiers and MAC addresses associated with peer bridges using the shortest paths determined for the VLANs; and
the forwarding element is operable to perform a RPFC for the incoming packet, the RPFC being considered a failure when the incoming packet arrives on a port which does not match an egress port associated in the FIB with a VLAN identifier and the source MAC address of the incoming packet.
26. An Ethernet bridge as defined in claim 25 , wherein the shortest path algorithm is operable according to a first ranking algorithm for a first VLAN and according to a second ranking algorithm for a second VLAN.
27. An Ethernet bridge as defined in claim 16 , wherein the forwarding element is operable to temporarily disable the RPFC for unicast traffic when the link state information changes.
28. An Ethernet bridge as defined in claim 16 , wherein the shortest path algorithm employs symmetric link metrics.
29. An Ethernet bridge as defined in claim 16 , wherein the FIB is populated with egress ports and MAC addresses associated with a peer bridge only for selected shortest paths between the peer bridge and other bridges, each selected path including the bridge and being between the peer bridge and a bridge that is in at least one community of interest with the peer bridge.
30. An Ethernet bridge as defined in claim 16 , wherein the FIB is populated with at least one multicast MAC address.
31. A method of operating an Ethernet bridge, comprising:
exchanging link state information with peer bridges, wherein the link state information comprises MAC addresses associated with peer bridges;
determining shortest paths between bridges based on the exchanged link state information using a shortest path algorithm which 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 such that connectivity between the two bridges follows the same path in both directions;
populating a forwarding information base (FIB) with egress ports, VLAN identifiers and MAC addresses associated with peer bridges using the determined shortest paths;
performing a reverse path forwarding check (RPFC) for the incoming packet, the RPFC being considered a failure when the incoming packet arrives on a port which does not match an egress port associated in the FIB with a VLAN identifier and a source MAC address of the incoming packet; and
discarding the incoming packet when the RPFC of the incoming packet is considered a failure.
32. An Ethernet bridge, comprising:
a routing element operable:
to exchange link state information with peer bridges, wherein the link state information comprises MAC addresses associated with peer bridges; and
to determine shortest paths between bridges based on the exchanged link state information using a shortest path algorithm which 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 such that connectivity between the two bridges follows the same path in both directions;
a forwarding information base (FIB) populated with egress ports, VLAN identifiers and MAC addresses associated with peer bridges using the determined shortest paths; and
a forwarding element operable:
to perform a reverse path forwarding check (RPFC) for the incoming packet, the RPFC being considered a failure when the incoming packet arrives on a port which does not match an egress port associated in the FIB with a VLAN identifier and a source MAC address of the incoming packet; and
to discard the incoming packet when the RPFC of the incoming packet is considered a failure.