Network path selection for multi-homed edges to ensure end-to-end resiliency

A first router that is a member of a first multi-homing set of a plurality of routers in a layer three (L3) network each connected to a first layer two (L2) network with a respective one of a plurality of first access links to provide a first service to the first L2 network, wherein the first router comprises:

• a pseudowire setup module to establish one or more core links to interconnect the plurality of routers in the first multi-homing set to one or more routers of a plurality of routers in the L3 network in a second multi-homing set, wherein each router in the second multi-homing set is connected to the second L2 network with a respective one of a plurality of second access links, wherein one of the core links has an active status to transport first service data traffic;
• an access link monitor to store a plurality of access link condition records, wherein each access link condition record comprises a state field that denotes whether a corresponding access link is operational with respect to the first service and a status field that denotes whether the corresponding access link is designated active for transporting the first service data traffic, wherein the plurality of access link condition records stored by the access link monitor includes a corresponding access link condition record for each of the first access links and for each of the second access links;
• a core link database to store a plurality of core link condition records, wherein each core link condition record comprises a state field that denotes whether a corresponding one of the core links is operational with respect to the first service, a locally advertised field that denotes a status of one of the first access links that connects to a router in the first multi-homing set that is connected to the corresponding one of the core links, and a peer advertised field that denotes a status of one of the second access links that connects to a router in the second multi-homing set that is connected to the corresponding one of the core links;
• a connection check module to detect failures of one or more of the core links connected to the first router and to set the state fields of core link condition records in core link database that correspond to the failed core links to a down value;
• a path selection policy;
• a plurality of interface cards to send and receive packets;
• a switch module to switch a status of one of the first access links to activate to transport first service data traffic;
• and
• a path selector to apply the path selection policy,
• wherein the connection check module detects a failure of one of the core links, and
• wherein the path selector, in response the failure, applies the path selection policy to the core link database to select one of the core links to activate to transport first service data traffic and to direct the switch module to switch to active a status of one of the first access links that connects to the router in the first multi-homing set that connects to the selected core link.

A system comprising:

• a first layer two (L2) network;
• a second L2 network;
• a first multi-homing set comprising a plurality of routers in a layer three (L3) network, wherein each of the plurality of routers is connected to the first L2 network with a respective one of a plurality of first access links to provide a first service to the first L2 network;
• a second multi-homing set comprising a plurality of routers in a L3 network, wherein each of the plurality of routers is connected to the second L2 network with a respective one of a plurality of second access links to provide the first service to the second L2 network;
• and
• a plurality of core links to interconnect the plurality of routers in the first multi-homing set with the plurality of routers in the second multi-homing set,
• wherein a first router in the first multi-homing set comprises a first core link database to store a plurality of core link condition records, wherein each core link condition record comprises a state field that denotes whether a corresponding one of the core links is operational with respect to the first service, a locally advertised field that denotes a status of one of the first access links that connects to a router in the first multi-homing set that is connected to the corresponding one of the core links, and a peer advertised field that denotes a status of one of the second access links that connects to a router in the second multi-homing set that is connected to the corresponding one of the core links,
• wherein the first router in the first-multihoming set stores a plurality of access link condition records, wherein each access link condition record comprises a state field that denotes whether a corresponding access link is operational with respect to the first service and a status field that denotes whether the corresponding access link is designated as active for transporting first service data traffic, wherein the plurality of access link condition records stored by the first router includes a corresponding access link condition record for each of the first access links and for each of the second access links,
• wherein, upon failure of a first one of the core links, the first router selects one of the core links to activate to transport first service data traffic when the core link condition record in the first core link database corresponding to the selected core link has a locally advertised field set to active status, and switches to active a status of a standby one of the first access links that connects to one of the routers in the first multi-homing that is also connected to the selected core link,
• wherein a second router in the second multi-homing set comprises a second core link database to store a plurality of core link condition records, and
• wherein, upon failure of the first one of the core links, the second router selects the core link selected by the first router to activate to transport first service data traffic when the core link condition record in the second core link database corresponding to the selected core link has a peer advertised field set to active status.