The document discusses segment routing and its use for inter-domain connectivity at scale. Segment routing allows source routing by encoding a path as an ordered list of segments in packet headers. It can be used to interconnect massive-scale datacenters and networks with hundreds of thousands of nodes. Segment routing scales through the use of globally unique prefix segments, redistribution of routing information only from the core to edges, and segment routing path computation elements. The path computation elements use segment routing native algorithms to optimize paths while maintaining equal-cost multipath routing.