PMSR - Poor Man's Segment Routing, a minimalistic approach to Segment Routing and a Traffic Engineering use case

TL;DR

PMSR offers a minimalistic, easy-to-implement alternative to traditional Segment Routing by eliminating the need for protocol enhancements, simplifying control plane operations, and supporting most current SR use cases, with an open source prototype and an optimized path assignment algorithm.

Contribution

The paper introduces PMSR, a simplified Segment Routing approach that requires no protocol modifications, along with a proven optimal traffic engineering path assignment algorithm.

Findings

PMSR reduces complexity compared to traditional SR.

PMSR supports most SR use cases.

An open source PMSR prototype was developed.

Abstract

The current specification of the Segment Routing (SR) architecture requires enhancements to the intra-domain routing protocols (e.g. OSPF and IS-IS) so that the nodes can advertise the Segment Identifiers (SIDs). We propose a simpler solution called PMSR (Poor Man's Segment Routing), that does not require any enhancement to routing protocol. We compare the procedures of PMSR with traditional SR, showing that PMSR can reduce the operation and management complexity. We analyze the set of use cases in the current SR drafts and we claim that PMSR can support the large majority of them. Thanks to the drastic simplification of the Control Plane, we have been able to develop an Open Source prototype of PMSR. In the second part of the paper, we consider a Traffic Engineering use case, starting from a traditional flow assignment optimization problem which allocates hop-by-hop paths to flows. We propose a SR path assignment algorithm and prove that it is optimal with respect to the number of segments allocated to a flow.