Method and apparatus establishing forwarding state using path state advertisements
View Patent ↗Paths may be advertised on a network implementing a link state routing protocol by using path state advertisement that are distributed in the same manner as link state advertisements. The path state advertisements contain path entries, each of which includes a globally unique path ID and path information such as a series of nodes or links that defines the path through the network. When a path state advertisement is received by a network element, the network element will evaluate the path entries in the path state advertisement to determine if the path state advertisement is relevant and, if necessary, install forwarding state for the relevant path entries. Path state advertisements not relevant to a network element are not used to affect forwarding state on the network element. Label based forwarding may then be used by the network elements to forward data along the path, in which the globally unique path ID is used as the label for the data.
1. A network element, comprising:
a forwarding plane; and
a control plane, the control plane containing at least one processor containing control logic configured to implement a link state routing process to enable the network element to receive and forward link state advertisements to enable the link state advertisements to be flooded on the network, the link state routing process further being configured to enable the network element to receive and forward path state advertisements to enable the path state advertisements to be flooded on the network as if they were link state advertisements in the link state routing protocol;
wherein the path state advertisements comprise at least one path entry, the path entry relating to a previously calculated proposed path to be established through at least a portion of a communication network and including at least a path identifier and path information defining the previously calculated path that is to be established through the portion of the communication network.
2. The network element of claim 1 , wherein the link state routing process is further configured to parse the received path state advertisements for path entries that reference the network element or that reference at least one link connected to the network element, and to cause forwarding state to be installed on the network element for those entries that reference the network element or that reference at least one link connected to the network element, the forwarding state enabling the network element to forward traffic on the paths associated with the entries that reference the network element.
3. The network element of claim 2 , wherein the link state routing process is further configured to extract from the path state advertisement information that the network element will need to use to cause the forwarding state to be installed on the network element.
4. A network element, comprising:
a forwarding plane; and
a control plane, the control plane containing at least one processor containing control logic configured to implement a link state routing process to enable the network element to receive and forward link state advertisements to enable the link state advertisements to be flooded on the network, and control logic further configured to enable the network element to receive and forward path state advertisements to enable the path state advertisements to be flooded on the network as if they were link state advertisements in the link state routing protocol;
wherein the path state advertisements comprise at least one path entry, the path entry relating to a previously calculated proposed path to be established through at least a portion of a communication network and including at least a path identifier and path information defining the previously calculated path that is to be established through the portion of the communication network;
wherein the control logic is further configured to parse the received path state advertisements for path entries that reference the network element or that reference at least one link connected to the network element, and to install forwarding state on the network element for those entries that reference the network element or that reference at least one link connected to the network element, the forwarding state enabling the network element to forward traffic on the paths associated with the entries that reference the network element; and
wherein the control logic is further configured to parse the received path state advertisements for path entries that reference the network element or that reference at least one link connected to the network element, and to not install forwarding state on the network element for any path where the path information for the path contained in the path state advertisement does not reference the network element and does not reference at least one link connected to the network element.
5. The network element of claim 2 , wherein the path state advertisements contain path information defining multiple previously calculated paths that are to be established through the portion of the communication network.