Computing Delay-Constrained Least-Cost Paths for Segment Routing is Easier Than You Think

TL;DR

This paper introduces BEST2COP, an efficient algorithm for computing delay-constrained least-cost paths in Segment Routing networks, addressing real-time application needs with scalable and accurate solutions.

Contribution

We present BEST2COP, the first exact, ECMP-aware algorithm tailored for delay-constrained path computation in SR, leveraging delay measurement limitations and SR constraints.

Findings

BEST2COP scales well in large networks

Returns all DCLC solutions in less than a second for networks with thousands of destinations

Outperforms heuristic methods in accuracy and efficiency

Abstract

With the growth of demands for quasi-instantaneous communication services such as real-time video streaming, cloud gaming, and industry 4.0 applications, multi-constraint Traffic Engineering (TE) becomes increasingly important. While legacy TE management planes have proven laborious to deploy, Segment Routing (SR) drastically eases the deployment of TE paths and thus became the most appropriate technology for many operators. The flexibility of SR sparked demands in ways to compute more elaborate paths. In particular, there exists a clear need in computing and deploying Delay-Constrained Least-Cost paths (DCLC) for real-time applications requiring both low delay and high bandwidth routes. However, most current DCLC solutions are heuristics not specifically tailored for SR. In this work, we leverage both inherent limitations in the accuracy of delay measurements and an operational constraint added by SR. We include these characteristics in the design of BEST2COP, an exact but efficient ECMP-aware algorithm that natively solves DCLC in SR domains. Through an extensive performance evaluation, we first show that BEST2COP scales well even in large random networks. In real networks having up to thousands of destinations, our algorithm returns all DCLC solutions encoded as SR paths in way less than a second.