Topology discovery, control channel establishment, and datapath provisioning within an aggregation network with centralized control

A method comprising:

• by an aggregation node of a plurality of aggregation nodes of a network, executing a control plane protocol to discover neighboring ones of the aggregation nodes of the network;
• by the aggregation node, sending flood messages to discovered local neighbor nodes toward a centralized controller network device to establish a Source Routed Tunnel (SRT) control channel between the aggregation node and the centralized controller network device;
• by the aggregation node, sending Keepalive packets to the centralized controller network device to ensure a state of the SRT control channel;
• responsive to determining that no Keepalive Reply is received from the centralized controller network device within a time period, and by the aggregation node, generating a new Flood message with a new generation number to force acceptance at the centralized controller network device of a new SRT control channel;
• receiving, by the aggregation node, a message from the centralized controller network device via the established SRT control channel, wherein the message specifies directed Forwarding Information Base (FIB) state pre-computed by the centralized controller network device for configuring a forwarding plane of the aggregation node;
• and
• responsive to receiving the message, and by the aggregation node, installing the directed FIB state received in the message, wherein the directed FIB state comprises one or more Multiprotocol Label Switching (MPLS) labels for the aggregation node to use for sending packets on an Label Switched Path (LSP).

A computer-readable storage medium comprising instructions to cause a programmable processor to:

• execute a control plane protocol on a processor of a network device to discover neighboring ones of a plurality of nodes of a network;
• responsive to receiving flood messages and determining that the flood messages do not include a layer two address for the network device, modify the flood messages by updating an intermediate node list of each of the flood messages to include a layer two address of the network device, wherein the intermediate node list of each of the flood messages specifies layer two addresses and interfaces for all nodes that the respective flood message traversed within the network;
• send the modified flood messages to discovered local neighbor nodes toward a centralized controller network device to establish a Source Routed Tunnel (SRT) control channel between the network device and the centralized controller network device;
• receive, at the network device, a message from the controller via the established SRT control channel, wherein the message specifies directed Forwarding Information Base (FIB) state pre-computed by the centralized controller network device for configuring a forwarding plane of the aggregation node;
• and
• responsive to receiving the message, install the directed FIB state received in the message within a forwarding component of the network device, wherein the directed FIB state comprises one or more Multiprotocol Label Switching (MPLS) labels for the network device to use for sending packets on an Label Switched Path (LSP).

A network device comprising:

• a plurality of network interfaces to send and receive network packets;
• a forwarding component that provides a data plane to perform label operations on the network packet to forward the network packets on label switched paths through a network;
• and
• a control unit executing a control protocol to:
• discover neighboring nodes of a plurality of nodes of the network,
• responsive to receiving flood messages and determining that the flood messages do not include a layer two address for the network device, modify the flood messages by updating an intermediate node list of each of the flood messages to include a layer two address of the network device, wherein the intermediate node list of each of the flood messages specifies layer two addresses and interfaces for all nodes that the respective flood message traversed within the network,
• send the modified flood messages to discovered neighbor nodes toward a centralized controller to establish a Source Routed Tunnel (SRT) control channel between the network device and the centralized controller, and
• receive, from the centralized controller and via the SRT control channel, forwarding information for transporting the network packets along one or more transport label switched paths (LSPs) within the network.