**Session Date/Time:** 17 Mar 2026 08:00

# [PCE](../wg/pce.html)

**IETF 125 - Shenzhen, China**

## Summary
The Path Computation Element (PCE) Working Group met during IETF 125 to discuss the status of active drafts and several new proposals. Key focus areas included Segment Routing (SR) policy extensions, stateful PCE enhancements (specifically regarding multipath and orphan LSP handling), and extensions for optical and fine-grain transport networks. Three documents are currently in the RFC Editor queue, and several others are nearing Working Group Last Call (WGLC). The group emphasized the need for operational and implementation sections in all maturing drafts.

## Key Discussion Points

### 1. Introduction and Document Status
**Julien Meuric** and **Dhruv Dhody** provided an overview of the WG's progress:
*   Three IDs are in the RFC Editor queue: `draft-ietf-pce-multipath` (pending), `draft-ietf-pce-pcep-extension-pce-controller-sr`, and a bidirectional SR extension.
*   `draft-ietf-pce-flexible-grid`: **Huaimo Chen** confirmed that comments from the WGLC are still pending and an update will be published soon.
*   `draft-ietf-pce-pcep-extension-pce-controller-sr`: **Yisong Han** has joined as shepherd; review is pending.
*   `draft-ietf-pce-state-sync`: **Andrew Stone** is now shepherding and will perform a review post-IETF 125.

### 2. Stateful PCE Extensions

#### 2.1 [WGLC changes for multi-path](https://datatracker.ietf.org/meeting/125/materials/slides-125-pce-21-wglc-changes-for-multi-path-00)
**Samuel Sidor** presented updates for `draft-ietf-pce-multipath`. 
*   **Changes:** Updates to RBNF for `PCInitiate` and stateful messages, introduction of the `PATH-ATTRIB` object, and clarification that point-to-point protection is out of scope for the backup TLV.
*   **Discussion:** **Adrian Farrel** (Shepherd) noted the draft is stable and nearing completion, pending a final check once authors finish the current update cycle.

#### 2.2 [Performance Measurements](https://datatracker.ietf.org/meeting/125/materials/slides-125-pce-pcep-extensions-for-performance-measurements-for-sr-te-and-mpls-te-lsps-with-stateful-pce-00)
**Rakesh Gandhi** proposed extensions for end-to-end monitoring of delay, loss, liveness, and bandwidth.
*   **Discussion:** **Andrew Stone** raised concerns regarding "message explosion" if standard `PCRpt` messages are used for high-frequency statistics. He suggested evaluating a new informational message type to avoid the overhead of full path state reporting.

#### 2.3 [Amendment to Stateful PCE](https://datatracker.ietf.org/meeting/125/materials/slides-125-pce-23-amendment-to-stateful-pce-00)
**Andrew Stone** discussed updates to stateful PCE procedures, specifically addressing "orphan LSPs" (LSPs without delegation after a PCE failure).
*   **Proposal:** Change RFC 8231 text from "may attempt to redelegate" to "must attempt to redelegate" to provide a standardized behavior for PCCs.
*   **Discussion:** **Dhruv Dhody** highlighted the importance of the operational section for this change.

#### 2.4 [LSP State Reporting](https://datatracker.ietf.org/meeting/125/materials/slides-125-pce-24-lsp-state-reporting-00)
**Samuel Sidor** presented new flags: the X-flag (explicit path source) and the T-flag (Transit Eligible).
*   **Discussion:** **Li Zhang** questioned the necessity of the T-flag given existing Binding SID (BSID) RFCs. **Samuel Sidor** and **Andrew Stone** clarified that while existing RFCs cover BSID allocation, the T-flag explicitly signals to the PCE whether a BSID is eligible to be used as a transit SID in *other* path computations.

### 3. Segment Routing (SR)

#### 3.1 [SR P2MP Policy](https://datatracker.ietf.org/meeting/125/materials/slides-125-pce-31-sr-p2mp-policy-00)
**Hooman Bidgoli** provided an update on `draft-ietf-pce-sr-p2mp-policy`.
*   **Changes:** Updated operational considerations regarding scaling and liveness detection.
*   **Discussion:** **Dhruv Dhody** and **Zafar Ali** suggested focusing specifically on the PCEP protocol's role in liveness detection and referencing other working group documents (e.g., PIM) for general Fast Reroute (FRR) mechanisms to avoid overlap.

#### 3.2 [SRv6 Inter-layer network programming](https://datatracker.ietf.org/meeting/125/materials/slides-125-pce-32-srv6-inter-layer-network-programming-00)
**Minshe Wang** proposed a new Node Attribute Identifier (NAI) for the `End.IL` SID.
*   **Discussion:** **Dhruv Dhody** requested a figure or example in the next version to illustrate how the underlay tunnel ID is utilized during path setup.

#### 3.3 [SRv6 Policy SID List Optimization](https://datatracker.ietf.org/meeting/125/materials/slides-125-pce-path-computation-element-communication-protocol-pcep-extensions-for-srv6-policy-sid-list-optimization-draft-all-pce-srv6-policy--00)
**Zafar Ali** requested adoption for extensions allowing the skipping of the endpoint Node SID in specific SRv6 scenarios. This work follows the adoption of the base requirement in the SPRING WG.

#### 3.4 [MSD Consideration](https://datatracker.ietf.org/meeting/125/materials/slides-125-pce-msd-consideration-in-path-computation-element-communication-protocol-pcep-draft-ali-pce-sr-policy-msd-consideration-00)
**Zafar Ali** presented a merged draft covering both SR-MPLS and SRv6 Maximum SID Depth (MSD) relaxations when the first SID is an Adjacency SID.
*   **Discussion:** The group discussed whether to progress this as a new document or a `bis` update to the base SR PCEP specifications.

### 4. Topology and Miscellaneous

#### 4.1 [PCEP-LS Optical](https://datatracker.ietf.org/meeting/125/materials/slides-125-pce-draft-lee-pce-pcep-ls-optical-00)
**Shu Xu** presented extensions for `draft-ietf-pce-pcep-ls` to support optical node and link attributes.
*   **Discussion:** **Zafar Ali** expressed concern over overlap with BGP-LS. **Adrian Farrel** and **Dhruv Dhody** noted that `draft-ietf-pce-pcep-ls` is an experimental track document, and this extension continues that experiment for environments where BGP is not deployed.

#### 4.2 [Fine Grain Transport](https://datatracker.ietf.org/meeting/125/materials/slides-125-pce-42-fine-grain-transport-00)
**Minshe Wang** proposed extensions for FG-MTN (Fine Grain Metro Transport Network) topology reporting and path setup.
*   **Coordination:** **Fatai Zhang** (CCAMP Chair) confirmed that the PCEP protocol extensions are within the scope of the PCE WG, while the underlying technology is managed by CCAMP and ITU-T.

#### 4.3 [Bounded Latency](https://datatracker.ietf.org/meeting/125/materials/slides-125-pce-slides-for-draft-xiong-pce-detnet-bounded-latency-07-125-00)
**Minshe Wang** presented updates to align PCEP metrics with DetNet standards (RFC 8655 and RFC 9320).
*   **Next Steps:** The chairs will coordinate with the DetNet WG chairs before moving forward with adoption.

## Decisions and Action Items
*   **Merge:** The authors of the SR-MPLS and SRv6 MSD drafts have merged their work into a single document (`draft-ali-pce-sr-policy-msd-consideration`).
*   **Shepherding:** **Andrew Stone** to complete the shepherd review for `draft-ietf-pce-state-sync`.
*   **Update Required:** **Huaimo Chen** to update `draft-ietf-pce-flexible-grid` to address pending WGLC comments.

## Next Steps
*   Chairs to issue a call for adoption for the Performance Measurement and Stateful Amendment proposals after further list discussion.
*   Chairs to discuss the priority of the "Unordered Queue" documents based on implementation feedback from the WG.
*   Authors of `draft-ietf-pce-sr-p2mp-policy` to refine liveness detection text to focus strictly on PCEP's role.