Fast Reoptimization With Only a Few Changes: Enhancing Tactical Traffic Engineering With Segment Routing Midpoint Optimization

Recent advancements in the context of Segment Routing (SR) have shown that the Midpoint Optimization (MO) concept enables a substantial reduction in the number of SR policies required to implement Traffic Engineering (TE) configurations. In this paper, we demonstrate that this concept can also be applied to the use case of tactical TE to considerably reduce the number of network changes required to react to critical events, thereby facilitating lower provisioning times and a generally improved time-to-repair. For this, we develop MOLS, a Local Search-based optimization routine that is able to provide close to optimal solutions within just a couple of seconds. The latter is shown based on extensive evaluations featuring various real-world topologies, including data from the backbone of a Tier-1 Internet Service Provider. Compared to state-of-the-art approaches relying on conventional SR, MOLS achieves similar or better solution quality while requiring substantially fewer configuration changes to implement the respective solutions. Furthermore, MOLS is able to resolve over 99% of overutilization scenarios resulting from different failure types, mostly within sub-second fashion and with an exceptionally small number of changes. Lastly, we also extend MOLS to adhere to specified latency bounds while even fixing initially violated ones.