An Extended Look at Midpoint Optimization for Segment Routing

In this paper, we discuss and examine the concept of Midpoint Optimization (MO) for Segment Routing (SR). It is based on the idea of integrating SR policies into the Interior Gateway Protocol (IGP) to allow various demands to be steered into them. We discuss the benefits of this approach when compared to end-to-end SR and potential challenges that might arise in deployment. We further develop a Linear Program-based optimization algorithm to assess the Traffic Engineering capabilities of MO for SR. Based on traffic and topology data from a Tier-1 Internet Service Provider as well as other, publicly available data, we show that, for most problem instances, this algorithm is able to achieve (close to) optimal results with regards to the maximum link utilization, that are on par with state-of-the-art end-to-end SR approaches. However, our MO approach requires substantially less policies to do so. For some instances, the achieved reduction ranges up to more than 99%. Furthermore, we show that latency bounds for individual demands can be incorporated into our algorithm without significantly worsening the quality of solutions. This is a crucial finding as the inclusion of latency bounds is a basically mandatory requirement for traffic engineering algorithms to be used in many real-world networks.