SRIFT: Segment Routing in Fat Trees

This document specifies signaling procedures for Segment Routing in RIFT. Each node's loopback address, Segment Routing Global Block (SRGB) and Node Segment Identifier (Node-SID), which are typically assigned by a configuration management system and distibuted by routing protocols, are distributed southbound from the Top Of Fabric (TOF) nodes via RIFT's Key-Value distribution mechanism, so that each node can compute how to reach a segment represented by the active SID in a packet. An SR controller signals SR policies to ingress nodes so that they can send packets with a desired segment list to steer traffic.