RFC 9514 defines extensions to the Border Gateway Protocol - Link State (BGP-LS) for carrying SRv6 information. BGP-LS (RFC 7752, updated by RFC 9552) is used to export link-state topology and traffic engineering information from IGP domains to external consumers such as SDN controllers and Path Computation Elements (PCEs). This RFC extends BGP-LS to include SRv6-specific attributes.
The extensions enable a centralized controller to learn the complete SRv6 topology of the network, including SRv6 capabilities, locators, End SIDs, adjacency SIDs (End.X), and the SID structure. With this information, a controller can compute SRv6 paths and program SR Policies without needing to participate in the IGP directly.
This is a critical building block for SDN-based SRv6 deployments where a PCE or SDN controller computes paths centrally and distributes them via PCEP or BGP SR Policy. The BGP-LS SRv6 extensions ensure the controller has a complete and accurate view of the SRv6 data plane.
+------------------+
| SDN Controller | BGP-LS provides the SRv6 topology database
| / PCE | to the controller, which then computes
+--------+---------+ paths and programs SR Policies via PCEP
| or BGP SR Policy.
BGP-LS Session
|
+--------+---------+
| BGP-LS Speaker | Collects IGP SRv6 data from IS-IS/OSPFv3
| (Route Reflector) and exports via BGP-LS to the controller.
+--------+---------+
|
IGP Domain (IS-IS or OSPFv3 with SRv6 extensions)
Component
Role
BGP-LS Speaker
Collects SRv6 information from the IGP and exports it northbound
SDN Controller / PCE
Consumes the BGP-LS SRv6 topology to compute constrained paths
PCEP / BGP SR Policy
Southbound protocol to push computed SR Policies to headend routers
Common Pitfalls
BGP-LS SRv6 extensions only export information -- they do not program the data plane. A separate mechanism (PCEP, BGP SR Policy) is needed to install computed paths.
The BGP-LS speaker must participate in the IGP to learn SRv6 TLVs. If the IGP peering is misconfigured or the IGP does not carry SRv6 extensions, BGP-LS will have an incomplete view.
Ensure the BGP-LS speaker's IGP implementation supports the SRv6-specific TLVs from RFC 9352 (IS-IS) or RFC 9513 (OSPFv3). Older implementations may silently drop unknown TLVs.
The SRv6 SID Structure TLV is essential for the controller to correctly parse the LOC:FUNC:ARG boundaries. Missing SID Structure information can lead to incorrect path computation.
Multi-domain deployments require BGP-LS from each domain. The controller must stitch cross-domain topology views to compute end-to-end SRv6 paths.