**Session Date/Time:** 19 Mar 2026 03:30

# [LSVR](../wg/lsvr.html)

## Summary
The LSVR (Link State Vector Routing) Working Group met at IETF 125 in Shenzhen. The session focused on the status of the BGP-LS YANG model, the strategic direction for Link Layer Discovery (specifically choosing between L3DL and L3ND), and extensions for BGP-LS-SPF to support SRv6 and policy state synchronization. Key administrative items included addressing outstanding errata on RFC 9015 and the need for a response to an IEEE liaison.

## Key Discussion Points

### WG Status and Administration
*   **Errata:** Two errata (one technical, one editorial) have been filed against RFC 9015. **Acee Lindem** and **Keyur Patel** committed to reviewing and verifying these.
*   **Liaison:** A liaison from the IEEE has been pending for a year. The chairs noted a response is required and will be informed by the decision on the L3DL/L3ND direction.
*   **Draft Status:** `draft-ietf-lsvr-bgp-ls-yang` has been updated to version 03.

### [1. A YANG Model for BGP-LS, BGP-LS-VPN, and BGP-LS-SPF](https://datatracker.ietf.org/meeting/125/materials/slides-125-lsvr-a-yang-model-for-bgp-ls-bgp-ls-vpn-and-bgp-ls-spf-00)
**Arvind Babu** presented updates to [draft-ietf-lsvr-bgp-ls-yang](https://datatracker.ietf.org/draft-ietf-lsvr-bgp-ls-yang/).
*   **Technical Updates:** The model has shifted from a TLV-centric representation to an NLRI-expanded structure to better handle variable-length, nested, and unknown TLVs. Known attributes now use explicit YANG types, while unknown ones are preserved as binary blobs for extensibility.
*   **Discussion:** **Mahesh Jethanandani** clarified that work on the BGP base model is parallel and not a blocking dependency for the BGP-LS parts. **Ketan Talaulikar** cautioned against BGP-LS becoming a "moving train" and suggested limiting the base model scope to RFC 9552, using augmentations for future extensions. The authors agreed to keep the base model focused.

### [2. L3DL & L3ND](https://datatracker.ietf.org/meeting/125/materials/slides-125-lsvr-2-l3dl-l3nd-00) / [L3DL and L3ND Straw man Direction](https://datatracker.ietf.org/meeting/125/materials/slides-125-lsvr-l3dl-and-l3nd-straw-man-direction-04)
**Keyur Patel**, **Acee Lindem**, and **Rob Shakir** discussed the path forward for link discovery.
*   **Protocol Choice:** The authors strongly recommended pursuing **L3ND** over L3DL. **Rob Shakir** noted that L3ND is significantly simpler as it uses standard TCP/TLS rather than a custom transport layer over raw Ethernet.
*   **Implementation Interest:** **Rob Shakir** questioned the current industry requirement for this work, noting author fatigue. **David Lamparter** indicated that L3ND would be much easier to implement in FRRouting than L2-based alternatives.
*   **Consensus Path:** The Chairs will use the mailing list to determine if there is sufficient interest to proceed with L3ND as a replacement for the expired L3DL work.

### [3. Applying BGP-LS Segment Routing over IPv6(SRv6) Extensions to BGP-LS-SPF](https://datatracker.ietf.org/meeting/125/materials/slides-125-lsvr-03-applying-bgp-ls-segment-routing-over-ipv6srv6-extensions-to-bgp-ls-spf-00)
**Li Zhang** presented updates on this individual draft.
*   **Technical Updates:** Added a new section on SRv6 SIDs and reachability, clarifying how locators and SIDs should be installed in the RIB/forwarding plane based on algorithm support and reachability checks.
*   **Discussion:** **Ketan Talaulikar** expressed that the document is stable and urged the working group to move to an adoption poll.

### [4. BGP-LS-SPF Extensions for SRv6 Policy State Synchronization](https://datatracker.ietf.org/meeting/125/materials/slides-125-lsvr-bgp-ls-spf-extensions-for-srv6-policy-state-synchronization-00)
**Wen Chenyang** presented a proposal for a new sub-TLV to indicate if an SRv6 SID is active in a policy.
*   **Discussion:** **Acee Lindem** questioned how non-head-end nodes would accurately know the active state of a SID in a policy. **Li Zhang** raised concerns regarding potential congestion if traffic steering decisions are made based on this state. **Jie Dong** requested the authors further clarify the specific use cases and benefits for path computation at the ingress node.

## Decisions and Action Items
*   **Action:** **Acee Lindem** and **Keyur Patel** to verify/respond to errata on RFC 9015.
*   **Action:** Chairs to initiate a discussion on the mailing list to choose between L3DL and L3ND.
*   **Action:** Chairs to initiate a response to the IEEE liaison following the L3DL/L3ND decision.

## Next Steps
*   Call for adoption poll for the "Applying BGP-LS SRv6 Extensions to BGP-LS-SPF" draft on the mailing list.
*   Authors of the BGP-LS-SPF Policy State draft to address comments regarding use cases and visibility on the mailing list.
*   Authors of `draft-ietf-lsvr-bgp-ls-yang` to continue aligning with IGP topology support in RFC 9552.