SR-MPLS Flexible Algorithm

Current network infrastructures, mainly for 5G services, employ differentiated traffic handling given constraints such as delay requirements, bandwidth, or path availability. In most cases, shortest‐path routing does not always evenly load the link traffic, causing congestion on critical links. Therefore, RFC 9350 introduced Flexible Algorithm (Flex‐Algo), which allows operators to proactively “slice” the network into multiple planes, each with their own routing rules and metrics. In our testing, we considered using three Flex‐Algo definitions—FA128, FA129, and FA130 to show different routing requirements. The FA128 prioritized paths with lower latency by using static or dynamic delay measurements to assess the path. The FA129 optimized traffic engineering (TE) metrics to balance link utilization among the available multiple links. Finally, we used FA130, which leveraged link affinities (or “colors”), a constraint that excludes certain links in the path computation. These enhancement measures are possible only because each node or router advertises its algorithm capabilities through the IGP. In IS-IS, these are presented in additional sub-TLVs and/or Application-Specific Link Attributes(ASLA) and assigned prefix SIDs mapped to the given Algorithm ID, making it possible to construct a novel logical topology given the constraints of the router. As defined in all three conditions, the routers successfully created paths and correctly installed them on MPLS forwarding tables, allowing end-to-end traffic to pass. This test confirms that Flex-Algo enables operators to deliver a good performance and resilience service class and simplifies configuration in SR‐MPLS environments.