Segment Routing for AI fabrics is a toolkit for deterministic traffic separation. The key practitioner takeaways:

• SRv6 SIDs are routable IPv6 addresses — no separate signalling protocol needed. IS-IS distributes locators; any node can reach any SID using normal IPv6 forwarding.
• uSID compression eliminates most of the SRH overhead concern. For 2-tier AI fabrics, a single uSID address carries the full path with zero additional headers.
• SR-TE maps application DSCP to fabric paths — NCCL traffic follows latency-optimised spines, checkpoint traffic follows throughput-optimised spines, with no application changes.
• EVPN+SRv6 simplifies multi-tenant design — the VPN SID encodes both destination and tenant context. No VTEPs, no VNI management, no VXLAN overhead.
• Flex-Algo runs multiple topology overlays on one physical fabric — latency-optimised and bandwidth-optimised paths coexist without separate hardware.
• MTU discipline is non-negotiable — always size fabric MTU for SRH overhead (add 56 bytes minimum for a 3-SID path) or use uSID to eliminate the overhead entirely.

Lab 14 gives you hands-on practice configuring and verifying an SR-TE policy that steers checkpoint traffic off the collective's spine path — the exact scenario AI fabric engineers encounter when mixed workloads share an infrastructure.