On the Benefits of Loops for Segment Routing Traffic Engineering

Over the recent years, Segment Routing (SR)-based Traffic Engineering (TE) received more and more attention in the research community. However, what has been mostly neglected so far is its capability to configure looping forwarding paths that visit nodes or even edges multiple times. In this paper, we show that, against intuition, the configuration of such loops can inherit (in some occasions significant) benefits with regards to common TE objectives if Equal Cost Multipath (ECMP) is used. This is not only illustrated on small theoretical examples but also confirmed for 2SR with real-world data from the backbone network of a Tier-1 Internet Service Provider, as well as other publicly available topologies.