Abstract: Multicast capabilities of a link state protocol controlled network are used to accelerate the flooding advertisement of topology change notifications within portions of the network. This flooding mechanism may be particularly efficient in a network with a large number of two-connected nodes such as a ring network architecture. A control plane specific multicast group address is used when flooding topology change notifications, and a process such as reverse path forwarding check is used as an additional control on forwarding of the notification to prevent looping of control plane packets. Two-connected nodes insert a forwarding entry into their FIB to enable frames containing the control message to be forwarded via the data plane on to the downstream node so that propagation of the control message along a chain of two-connected nodes may occur at data plane speeds.

Abstract: A resilient virtual Ethernet ring has nodes interconnected by working and protection paths. Each node has a set of VLAN IDs (VIDs) for tagging traffic entering the ring by identifying the ingress node and whether the traffic is on the working or protection path. MAC addresses are learned in one direction around the ring. A port aliasing module records in a forwarding table a port direction opposite to a learned port direction. Each node can also cross-connect working and protection paths. If a span fails, the two nodes immediately on either side of the failure are cross-connected to fold the ring. Working-path traffic is cross-connected onto the protection path at the first of the two nodes and is then cross-connected back onto the working path at the second of the two nodes so that traffic always ingresses and egresses the ring from the working path.

Abstract: Routes may be installed across multiple link state protocol controlled Ethernet network areas by causing ABBs to leak I-SID information advertised by BEBs in a L1 network area into an L2 network area. ABBs will only leak I-SIDs for BEBs where it is the closest ABB for that BEB. Where another ABB on the L2 network also leaks the same I-SID into the L2 network area from another L1 network area, the I-SID is of multi-area interest. ABBs will advertise I-SIDs that are common to the L1 and L2 networks back into their respective L1 network. Within each L1 and L2 network area, forwarding state will be installed between network elements advertising common interest in an ISID, so that multi-area paths may be created to span the L1/L2/L1 network areas. The L1/L2/L1 network structure may recurse an arbitrary number of times.

Abstract: Each equal cost path is assigned a path ID created by concatenating an ordered set of link IDs which form the path through the network. The link IDs are created from the node IDs on either set of the link. The link IDs are sorted from lowest to highest to facilitate ranking of the paths. The low and high ranked paths are selected from this ranked list as the first set of diverse paths through the network. Each of the link IDs on each of the paths is then renamed, for example by inverting either all of the high node IDs or low node IDs. After re-naming the links, new path IDs are created by concatenating an ordered set of renamed link IDs. The paths are then re-ranked and the low and high re-ranked paths are selected from this re-ranked list as the second set of diverse paths.

Abstract: An Ethernet network comprises nodes which support a plurality of different forwarding modes. A range of VLAN Identifiers (VIDs) are allocated to each of the forwarding modes. Connections are configured between a source node and a destination node of the network using different forwarding modes. Packets carrying data traffic are sent to the destination node by selectively setting a VID in a packet to a first value, to transfer a packet via a first connection and a first forwarding mode, and a second value to transfer a packet via the second connection and the second forwarding mode. Packets received from both of the connections and sent on to an end user. VLAN Identifiers can be allocated to different releases of functionality at nodes (e.g. software releases) such that packets are forwarded via a set of nodes supporting a first release, or via a set of nodes supporting a second release.

Abstract: A consistent tie-breaking decision between equal-cost shortest (lowest cost) paths is achieved by comparing an ordered set of node identifiers for each of a plurality of end-to-end paths. Alternatively, the same results can be achieved, on-the-fly, as a shortest path tree is constructed, by making a selection of an equal-cost path using the node identifiers of the diverging branches of the tree. Both variants allow a consistent selection to be made of equal-cost paths, regardless of where in the network the shortest paths are calculated. This ensures that traffic flow between any two nodes, in both the forward and reverse directions, will always follow the same path through the network.

Abstract: A method of installing forwarding state in a link state protocol controlled network node having a topology database representing a known topology of the network, and at least two ports for communication with corresponding peers of the network node. A unicast path is computed from the node to a second node in the network, using the topology database, and unicast forwarding state associated with the computed unicast path installed in a filtering database (FDB) of the node. Multicast forwarding state is removed for multicast trees originating at the second node if an unsafe condition is detected. Subsequently, a “safe” indication signal is advertised to each of the peers of the network node. The “safe” indication signal comprises a digest of the topology database. A multicast path is then computed from the network node to at least one destination node of a multicast tree originating at the second node.

Abstract: Virtual links may be used to divert traffic within an Ethernet network without affecting overall traffic patterns on the Ethernet network. In one embodiment, the virtual link may be established on the network via a routing system in use on the network. Nodes on a defined path for the virtual link will install forwarding state for the virtual link so that traffic may follow the defined path through the network. The logical view of the virtual link, from a routing perspective however, has the same cost as the shortest path between the endpoints of the virtual link and, accordingly, does not affect other traffic patterns on the network. Once established, the end nodes on the virtual path will have two equal cost paths through the network—one following the shortest path tree and one along the path for the virtual link. The end nodes may use a tie breaking process in an Equal Cost Multi Path (ECMP) selection process to preferentially select the virtual link over the shortest path.

Abstract: A method of multicast route computation in a link state protocol controlled network. A spanning tree is computed from a first node to every other node in the network using a known spanning tree protocol. The network is then divided into two or more partitions, each partition encompassing an immediate neighbour node of the first node and any nodes of the network subtending the neighbour node on the spanning tree. Two or more of the partitions are merged when a predetermined criterion is satisfied. Nodes within all of the partitions except a largest one of the partitions are then identified, and each identified node examined to identify node pairs for which a respective shortest path traverses the first node.

Abstract: A consistent tie-breaking decision between equal-cost shortest (lowest cost) paths is achieved by comparing an ordered set of node identifiers for each of a plurality of end-to-end paths. Alternatively, the same results can be achieved, on-the-fly, as a shortest path tree is constructed, by making a selection of an equal-cost path using the node identifiers of the diverging branches of the tree. Both variants allow a consistent selection to be made of equal-cost paths, regardless of where in the network the shortest paths are calculated. This ensures that traffic flow between any two nodes, in both the forward and reverse directions, will always follow the same path through the network.

Abstract: An Ethernet network comprises nodes which support a plurality of different forwarding modes. A range of VLAN Identifiers (VIDs) are allocated to each of the forwarding modes. Connections are configured between a source node and a destination node of the network using different forwarding modes. Packets carrying data traffic are sent to the destination node by selectively setting a VID in a packet to a first value, to transfer a packet via a first connection and a first forwarding mode, and a second value to transfer a packet via the second connection and the second forwarding mode. Packets received from both of the connections and sent on to an end user. VLAN Identifiers can be allocated to different releases of functionality at nodes (e.g. software releases) such that packets are forwarded via a set of nodes supporting a first release, or via a set of nodes supporting a second release.

Abstract: A method of installing forwarding state in a link state protocol controlled network node having a topology database representing a known topology of the network, and at least two ports for communication with corresponding peers of the network node. A unicast path is computed from the node to a second node in the network, using the topology database, and unicast forwarding state associated with the computed unicast path installed in a filtering database (FDB) of the node. Multicast forwarding state is removed for multicast trees originating at the second node if an unsafe condition is detected. Subsequently, a “safe” indication signal is advertised to each of the peers of the network node. The “safe” indication signal comprises a digest of the topology database. A multicast path is then computed from the network node to at least one destination node of a multicast tree originating at the second node.

Abstract: An Ethernet virtual switched sub-network (VSS) is implemented as a virtual hub and spoke architecture overlaid on hub and spoke connectivity built of a combination of Provider Backbone Transport (spokes) and a provider backbone bridged sub-network (hub). Multiple VSS instances are multiplexed over top of the PBT/PBB infrastructure. A loop free resilient Ethernet carrier network is provided by interconnecting Provider Edge nodes through access sub-networks to Provider Tandems to form Provider Backbone Transports spokes with a distributed switch architecture of the Provider Backbone Bridged hub sub-network. Provider Backbone transport protection groups may be formed from the Provider Edge to diversely homed Provider Tandems by defining working and protection trunks through the access sub-network.

Abstract: A method of multicast route computation in a link state protocol controlled network. A spanning tree is computed from a first node to every other node in the network using a known spanning tree protocol. The network is then divided into two or more partitions, each partition encompassing an immediate neighbor node of the first node and any nodes of the network subtending the neighbor node on the spanning tree. Two or more of the partitions are merged when a predetermined criterion is satisfied. Nodes within all of the partitions except a largest one of the partitions are then identified, and each identified node examined to identify node pairs for which a respective shortest path traverses the first node.

Abstract: An Ethernet switch for use in an Ethernet network comprises a set of ingress ports for receiving data frames and a set of egress ports. A memory is associated with each ingress port and stores forwarding information indicating one or more of the egress ports to which data frames received by that ingress port should be forwarded. A control or management interface receives information about a network connection established, or to be established, through the switch. A switch controller causes forwarding information to be stored in a memory associated with a first ingress port which the network connection will use, on the basis of the received information about a network connection. Forwarding information is not stored in a memory associated with a second of the set of ingress ports which the network connection will not use.

Abstract: An Ethernet virtual switched sub-network (VSS) is implemented as a virtual hub and spoke architecture overlaid on hub and spoke connectivity built of a combination of Provider Backbone Transport (spokes) and a provider backbone bridged sub-network (hub). Multiple VSS instances are multiplexed over top of the PBT/PBB infrastructure. A loop free resilient Ethernet carrier network is provided by interconnecting Provider Edge nodes through access sub-networks to Provider Tandems to form Provider Backbone Transports spokes with a distributed switch architecture of the Provider Backbone Bridged hub sub-network. Provider Backbone transport protection groups may be formed from the Provider Edge to diversely homed Provider Tandems by defining working and protection trunks through the access sub-network.

Abstract: MPLS networks offering PW or VPLS services may be interconnected with Ethernet networks implemented according to 802.1ah or 802.1Qay. The MPLS network may be a core and offer services to the Ethernet access networks, or vise-versa. Additionally, a mixture of different types of access networks may be interconnected by an MPLS core or an Ethernet core. Both network interworking and service interworking are provided. OAM fault detection may be implemented via maintenance entities extending across the network or end to end depending on the combination of networks and services offered by the networks.

Abstract: MPLS networks offering PW or VPLS services may be interconnected with Ethernet networks implemented according to 802.1ah or 802.1Qay. The MPLS network may be a core and offer services to the Ethernet access networks, or vise-versa. Additionally, a mixture of different types of access networks may be interconnected by an MPLS core or an Ethernet core. Both network interworking and service interworking are provided. OAM fault detection may be implemented via maintenance entities extending across the network or end to end depending on the combination of networks and services offered by the networks.

Abstract: MPLS networks offering PW or VPLS services may be interconnected with Ethernet networks implemented according to 802.1ah or 802.1Qay. The MPLS network may be a core and offer services to the Ethernet access networks, or vise-versa. Additionally, a mixture of different types of access networks may be interconnected by an MPLS core or an Ethernet core. Both network interworking and service interworking are provided. OAM fault detection may be implemented via maintenance entities extending across the network or end to end depending on the combination of networks and services offered by the networks.

Abstract: In an Ethernet network multiple point-to-multipoint (P2MP) trees are constructed to provide a P2MP service. Each tree provides service from a common root node to common leaves via different paths through the network. GMPLS signaling is utilized for configuring and maintaining the P2MP trees at each of the nodes in the network forming the respective tree. Each tree is constructed using a unique VID/MAC combination wherein the VID is unique to the tree and the MAC is associated with the multicast group identifying the P2MP membership. Traffic is forwarded through the network by the designated tree(s) by the VID/MAC DA combination by the common root node. The varying paths of each tree improves fault tolerance and enables redundancy and protection switching to be provided. Each tree of the service can be modified or repaired while traffic is still being routed through the remaining working tree(s), thus service impact is minimized.