LSR

Summary

The LSR Working Group session at IETF 119 in Brisbane was chaired by Yingzhen Qu, with Acee Lindem and Chris Hopps participating remotely. The session covered the status of active drafts, recent RFC publications, and several technical presentations regarding Layer 2 bundle member identifiers, YANG model updates, flood reduction measurements, power-conserving path strategies, and IGP extensions for sub-interface relationships.

Key Discussion Points

Working Group Status

Yingzhen Qu reported that four RFCs have been published since IETF 118, including OSPF/IS-IS Segment Routing YANG models and IGP unreachability prefix announcements.

draft-ietf-lsr-flood-reduction-arch has been adopted.
There was a discussion regarding the intended track for this draft. Tony Li indicated flexibility between Experimental and Informational. Gunter Van de Velde (AD) noted the IESG's preference for specific criteria for Experimental tracks but expressed pragmatism.
Gunter Van de Velde also emphasized that new adoptions should include specific milestones to satisfy IESG requirements regarding in-charter maintenance.

L2 Bundle Member Remote Identifiers

Lian presented updates on 02-Advertisement of Remote Interface Identifiers for Layer 2 Bundle Members regarding draft-ietf-lsr-l2-bundle-member-remote-id.

Updates include improved BGP-LS specifications, comprehensive security considerations, and corrections to how remote identifiers are acquired (clarifying LLDP Port ID TLV usage).
Jeff Tantsura suggested considering BFD for LAGs as a discovery mechanism. Acee Lindem and Les Ginsberg noted that while discovery is a prerequisite, the specific mechanism for discovery is out of scope for this IGP-focused draft.
The authors believe the draft is ready for Working Group Last Call (WGLC).

LSR YANG Update

Yingzhen Qu provided an update on 03-LSR_YANG_Update.

Several models are now published or in the RFC Editor queue.
The OSPF Flex-algo YANG model is with the AD for evaluation.
draft-ietf-lsr-isis-pics-yang, draft-ietf-lsr-isis-pics-l2member-attr-yang, and draft-ietf-lsr-isis-pics-srmpls-yang have been quiet and are nearing readiness for publication.
SRv6 models for OSPF and IS-IS are pending the base SRv6 model in the SPRING WG.

Flood Reduction Update and Measurements

Tony Przygienda presented flood reduction update measurements related to draft-ietf-lsr-flood-reduction-arch.

The "level/rank" concept for Hierarchical Sequence Number PDUs (HSNPs) was abandoned as it is not standardize-able across different peers and database states.
Technical analysis of hash collisions showed that a 48-bit Fletcher hash outperformed a 64-bit hash in clustering collisions far apart, making them practically irrelevant for database synchronization.
Tony Li and Tony Przygienda discussed why 48-bit hashes might be more effective due to node ID influence.

Power Conserving Path Placement Strategy (PCPPS)

Tony Li presented 5-A Power Conserving Path Placement Strategy (PCPPS) regarding [draft-mini-lsr-pcpps] and [draft-mini-lsr-power-group].

The strategy involves modifying CSPF to account for power consumption, allowing traffic to be consolidated onto fewer links so idle components can be powered down.
Les Ginsberg asked about customer demand; Tony Li asserted strong operator interest.
Zafar Ali raised concerns about metric consistency, normalization, and the relationship with the GREEN Working Group.
Tony Li argued that the metric (watts) is a standard physical unit and that head-ends do not need perfectly consistent algorithms to make local path decisions.
Acee Lindem suggested that [draft-mini-lsr-pcpps] belongs in TEAS, while the power group advertisement belongs in LSR.

Advertising IGP Measurement Groups

Derek Yeung presented 6-Advertising IGP Measurement Groups.

This draft proposes IGP auto-discovery for nodes participating in TWAMP or STAMP measurements.
Acee Lindem noted the similarity to S-BFD capability advertisements and agreed it fits within LSR.

Hierarchical SNPS

Tony Przygienda presented draft-prz-lsr-hierarchical-snps-01.

The presentation detailed the "gradient descent" analogy for database synchronization using HSNPs.
Extensive simulations (36 billion refreshes) were conducted to validate the robustness of the hashing mechanism against collisions.

Sub-interface Relationship Information

Li Zhang presented 08-IGP Extensions for Sub-interface Relationship Information.

The goal is to advertise the relationship between parent physical interfaces and sub-interfaces to prevent overloading shared physical bandwidth when multiple parallel VLANs are used.
Tony Li and Les Ginsberg questioned the architectural validity of the use case (running multiple IS-IS instances/adjacencies over parallel VLANs on the same link) and noted that existing bandwidth advertisements could likely solve the problem without new TLVs.

Decisions and Action Items

WGLC: The chairs will consider a WGLC for draft-ietf-lsr-l2-bundle-member-remote-id.
Adoption: A call for adoption will be considered for the Power Group draft after further list discussion.
Flood Reduction: The architecture draft will move forward as Experimental.

Next Steps

Tony Przygienda may investigate SipHash as an alternative to Fletcher hashes for HSNPs.
Li Zhang to provide more detailed use cases and address concerns regarding existing bandwidth advertisement mechanisms on the mailing list.
Kireeti Kompella flagged a forthcoming draft on MP-TE capabilities for a future meeting (likely Vienna).
Yingzhen Qu and chairs to start adoption calls for pending queue items post-IETF 119.

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