Utilizing domain segment identifiers for inter-domain shortest path segment routing

1. A method, comprising:

receiving, by an ingress network device associated with a first leaf domain network of a multi-domain network, a core domain network segment identifier associated with a core domain network of the multi-domain network;

receiving, by the ingress network device, location data of an egress network device associated with a second leaf domain network of the multi-domain network,

wherein the core domain network is a gateway from the first leaf domain network to the second leaf domain network, and

wherein the location data includes data identifying:

the core domain network segment identifier, wherein the core domain network segment identifier identifies a shortest path segment routing within the core domain network,

a second leaf domain network segment identifier associated with the second leaf domain network,

wherein the second leaf domain network segment identifier identifies a shortest path segment routing within the second leaf domain network, and

an egress network device segment identifier associated with the egress network device,

storing, by the ingress network device, the core domain network segment identifier and the location data; and

utilizing, by the ingress network device, the core domain network segment identifier and the location data to route traffic to the egress network device.

2. The method of claim 1 , wherein receiving the location data of the egress network device comprises:

receiving the location data of the egress network device via an advertisement with a segment list that includes the data identifying the core domain network segment identifier, the second leaf domain network segment identifier, and the egress network device segment identifier.

3. The method of claim 1 , further comprising:

receiving particular traffic destined for the egress network device;

determining a path for the particular traffic, through the multi-domain network and to the egress network device, based on the core domain network segment identifier and the location data; and

causing the particular traffic to be provided to the egress network device via the path.

4. The method of claim 3 , wherein determining the path for the particular traffic comprises:

determining a plurality of paths, through the multi-domain network and to the egress network device, based on the core domain network segment identifier and the location data; and

selecting the path, from the plurality of paths, based on a candidate path preference parameter.

5. The method of claim 3 , wherein the path includes a shortest label-switched path through the multi-domain network and to the egress network device.

6. The method of claim 1 , wherein the core domain network segment identifier is received from another border network device provided between the first leaf domain network and the core domain network.

7. The method of claim 1 , wherein the multi-domain network includes the core domain network and two or more leaf domain networks associated with the core domain network,

wherein the first leaf domain network and the second leaf domain network are included in the two or more leaf domain networks.

8. An ingress network device, comprising:

one or more memories; and

one or more processors to:

receive a core domain network segment identifier associated with a core domain network of a multi-domain network,

wherein the multi-domain network includes:

the core domain network,

a first leaf domain network associated with the core domain network and the ingress network device, and

a second leaf domain network;

receive location data of an egress network device associated with the second leaf domain network,

wherein the core domain network is a gateway from the first leaf domain network to the second leaf domain network, and

wherein the location data includes data identifying:

the core domain network segment identifier,

 wherein the core domain network segment identifier identifies a shortest path segment routing within the core domain network,

a second leaf domain network segment identifier associated with the second leaf domain network,

 wherein the second leaf domain network segment identifier identifies a shortest path segment routing within the second leaf domain network, and

an egress network device segment identifier associated with the egress network device;

store the core domain network segment identifier and the location data; and

utilize the core domain network segment identifier, the second leaf domain network segment identifier, and the egress network device segment identifier to route traffic to the egress network device.

9. The ingress network device of claim 8 , wherein the first leaf domain network is associated with a first leaf domain network segment identifier and the ingress network device is associated with an ingress network device segment identifier.

10. The ingress network device of claim 8 , wherein the one or more processors, when utilizing the core domain network segment identifier, the second leaf domain network segment identifier, and the egress network device segment identifier to route traffic to the egress network device, are to:

determine one or more shortest label-switched paths through the multi-domain network and to the egress network device based on the core domain network segment identifier, the second leaf domain network segment identifier, and the egress network device segment identifier; and

cause the traffic to be routed to the egress network device via the one or more shortest label-switched paths.

11. The ingress network device of claim 8 , wherein the one or more processors are further to:

receive particular traffic destined for a network device of the first leaf domain network;

determine a shortest label-switched path through the first leaf domain network and to the network device; and

cause the particular traffic to be provided to the network device via the shortest label-switched path.

12. The ingress network device of claim 8 , wherein the one or more processors are further to:

receive, from the egress network device, a tunnel encapsulation attribute,

wherein the one or more processors, when utilizing the core domain network segment identifier, the second leaf domain network segment identifier, and the egress network device segment identifier to route the traffic to the egress network device, are to:

utilize the core domain network segment identifier, the second leaf domain network segment identifier, the egress network device segment identifier, and the tunnel encapsulation attribute to route traffic to the egress network device via an encapsulated tunnel.

13. The ingress network device of claim 8 , wherein forwarding state information associated with the egress network device is locally stored in the second leaf domain network.

14. The ingress network device of claim 8 , wherein the one or more processors, when utilizing the core domain network segment identifier, the second leaf domain network segment identifier, and the egress network device segment identifier to route traffic to the egress network device, are to:

utilize the core domain network segment identifier, the second leaf domain network segment identifier, the egress network device segment identifier, and a shortest path first technique to route traffic to the egress network device.

15. A non-transitory computer-readable medium storing instructions, the instructions comprising:

one or more instructions that, when executed by one or more processors of an ingress network device, cause the one or more processors to:

receive a core domain network segment identifier associated with a core domain network of a multi-domain network,

wherein the ingress network device is associated with a first leaf domain network of the multi-domain network;

receive location data of an egress network device associated with a second leaf domain network of the multi-domain network,

wherein the core domain network is a gateway from the first leaf domain network to the second leaf domain network, and

wherein the location data includes data identifying:

the core domain network segment identifier,

 wherein the core domain network segment identifier identifies a shortest path segment routing within the core domain network,

a second leaf domain network segment identifier associated with the second leaf domain network,

 wherein the second leaf domain network segment identifier identifies a shortest path segment routing within the second leaf domain network, and

an egress network device segment identifier associated with the egress network device;

store the core domain network segment identifier and the location data;

receive traffic destined for the egress network device;

determine a path for the traffic, through the multi-domain network and to the egress network device, based on the core domain network segment identifier and the location data; and

cause the traffic to be provided to the egress network device via the path.

16. The non-transitory computer-readable medium of claim 15 , wherein the one or more instructions, that cause the one or more processors to receive the location data of the egress network device, cause the one or more processors to:

receive the location data of the egress network device via an advertisement with a segment list that includes the data identifying the core domain network segment identifier, the second leaf domain network segment identifier, and the egress network device segment identifier.

17. The non-transitory computer-readable medium of claim 15 , wherein the one or more instructions, that cause the one or more processors to determine the path for the traffic, cause the one or more processors to:

determine a plurality of paths for the traffic, through the multi-domain network and to the egress network device, based on the core domain network segment identifier and the location data; and

select the path, from the plurality of paths, based on a candidate path preference parameter.

18. The non-transitory computer-readable medium of claim 15 , wherein the path includes a shortest label-switched path through the multi-domain network and to the egress network device.

19. The non-transitory computer-readable medium of claim 15 , wherein the one or more instructions, when executed by the one or more processors, further cause the one or more processors to:

receive additional traffic destined for a network device of the first leaf domain network;

determine a shortest path through the first leaf domain network and to the network device; and

cause the additional traffic to be provided to the network device via the shortest path.

20. The non-transitory computer-readable medium of claim 15 , wherein the one or more instructions, when executed by the one or more processors, further cause the one or more processors to:

receive, from the egress network device, a tunnel encapsulation attribute,

wherein the one or more instructions, that cause the one or more processors to cause the traffic to be provided to the egress network device via the path, cause the one or more processors to:

utilize the tunnel encapsulation attribute to cause the traffic to be provided to the egress network device via an encapsulated tunnel.