Enabling Topology Visibility in BGP Fabrics with BGP-LS.

Why It Matters

Bringing BGP‑LS topology export into SONiC gives operators a vendor‑neutral way to do traffic engineering and fast reroute across multi‑datacenter AI interconnects, improving latency, capacity utilization and resilience. That capability directly addresses scaling and reliability challenges central to large AI training infrastructures.

Summary

Cisco and Alibaba presented work to add standardized topology visibility to SONiC using BGP-LS, enabling operators to export normalized network models (nodes, links, prefixes and SR info) from both IGP and hop-by-hop eBGP fabrics. The talk framed the need around AI DCI: multi‑data‑center fabrics require careful traffic engineering and fast‑reroute to meet RDMA/latency, bandwidth and disjointness requirements. The presenters argued BGP‑LS — contrary to a common misconception — can provide a full topology view in eBGP fabrics and scales as a multi‑vendor, standards‑based building block. They outlined how that topology data enables path computation and preinstalled backup paths for rapid failover in wide area DCI deployments.

Original Description

Presenter(s):

Ahmed Abdelsalam, Engineering Technical Leader, Cisco

Yijiao Qin, Software Engineer, Alibaba

Modern data center and fabric designs increasingly adopt BGP as the sole routing protocol to improve scalability and operational stability. However- this approach abstracts the underlying link and topology information- limiting the ability of controllers and automation systems to obtain a detailed network view comparable to traditional link-state protocols.

In this session- we present the design and implementation of BGP Link-State (BGP-LS) for BGP fabrics in FRR and its integration into SONiC. We will walk through the architectural choices- implementation challenges- and interoperability considerations involved in enabling routers to advertise topology information without relying on a traditional IGP.

The session will also cover the upstreaming of the BGP-LS implementation in FRR and the integration in SONiC: - https://github.com/FRRouting/frr/pull/20470 - https://github.com/FRRouting/frr/pull/20726