SR-MPLS Flexible Algorithm using new constraints (excl. Min Bandwidth, Max. delay and Reverse affinity)

As the networks develop to accommodate ultra‐low latency applications and allow more flexible control of used capacity, the basic IGP metrics are no longer sufficient. Two recent IETF proposals fill the existing gap by adding new Flex‐Algo constraints: Maximum Delay, forbids links whose delay exceeds the given value; exclude Minimum Bandwidth, which rules out links whose bandwidth is inferior to the given capacity value; and Exclude Reverse Affinity, forbids links which are colored by the "reverse affinity" color from the other end. We used FA131 for Maximum Delay, FA132 for Exclude Minimum Bandwidth, and FA133 for Exclude Reverse Affinity. 

Two DUTs were tested and connected to each other directly and with another router to provide various scenarios when possible constraints were imposed. While IS‐IS successfully advertised all the new constraints through sub‐TLVs, each of the Flex‐Algo aggregated a set of prefix SIDs of its own, and paths containing non‐conforming links for such constraints were removed, and the traffic was instead routed along the constraints of delay, bandwidth, or reverse‐affinity requirements. These new constraints generally enabled better service routing awareness of applications in the context of SR‐MPLS.