Traffic Engineering in Segment Routing Networks Using MILP

Abstract

In segment routing, a packet is forwarded along a path identified by a segment list. A segment list consists of segment identifiers (SIDs). A node-SID identifies a shortest-path segment, and an adjacency-SID identifies a link segment. A ${K}$ -segment path is a path with no more than ${K}$ segments. In this paper, we study the problem of finding a set of K- segment paths to carry all the flows in a given traffic matrix such that the maximum link utilization in the network is minimized. We first show that the solutions found by ${K}$ -LP, an existing linear programming (LP) approach, are not optimal because ${K}$ -LP does not support adjacency-SIDs. Focusing on 2-segment paths, a new LP formulation, denoted by e2-LP, is designed to support adjacency-SIDs in part. To fully support adjacency-SIDs, a mixed integer linear programming (MILP), denoted by ${K}$ -MILP, is designed. Since solving ${K}$ -MILP is time-consuming, a simplified version ( ${K}$ -sMILP) is also proposed. Finally, ${K}$ -sMILP is extended to prevent excessive flow splitting or using paths that are too long.