Segment routing has recently been proposed in the IETF toward making IP/MPLS networks service oriented while simplifying network operations. Segment routing computes paths at the source node using node identifiers and adjacency identifiers conjoined together to create a source-routed path. We propose a scalable transport paradigm as an enabler toward implementing segment routing in provider networks. We propose omnipresent Ethernet, our modification of carrier Ethernet (which is based on source-routed, binary-routed labels embedded in an Ethernet frame), to implement segment routing. We identify some of the scalability issues of the segment routing proposal in the context of source-routing overhead. To absolve scalability issues of segment routing, two routing schemes that implement multidomain source-routing techniques are proposed.

The hierarchical segment-routing (H-SR) scheme is proposed, which deploys a limited number of special nodes called swap nodes that are capable of label swapping to implement routing. The swap-node placement problem is formulated as an integer linear program to minimize the total routing distance within a network. Three heuristic techniques for swap-node selection based on centrality paradigms are presented. The H-SR scheme is further improved by a proposed multisegment-routing (M-SR) scheme that assumes all nodes in the network to be capable of label swapping. The H-SR and M-SR schemes are shown to significantly enhance the scalability of segment routing. A test-bed is built using carrier Ethernet hardware to support segment routing that validates the implementation of the proposed schemes. A simulation model to evaluate the schemes from a scalability perspective and their associated trade-offs is presented.

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