Session Date/Time: 18 Mar 2025 02:30

lsr

Summary

The LSR working group meeting covered a range of topics including updates on existing drafts, discussion of flooding reduction architectures, the ongoing debate around leader-based versus leaderless approaches, extensions for reverse prefix metrics, and extensions for load balancing. There were also updates on the LSR YANG modules and a new draft on energy-efficient routing. A key theme was the complexity of flooding optimization and the trade-offs between different approaches.

Key Discussion Points

Working Group Status Update: Discussed RFC publication, drafts in the IESG queue (OSPF admin tags, flex algo extensions for delay metrics, generic metric metric), and documents under consideration for working group last call (algorithm-related adjacency SIDs).
Flood Reduction Architecture: Shradha presented on the flood reduction architecture, emphasizing the need for incremental deployment and upgrade of flooding algorithms. The discussion focused on the definition of connected components, the role of zero-pruners, and how different versions of the same algorithm should be handled. The need for protocol extensions to advertise the active pruning algorithm and version was highlighted.
Leader-based vs. Leaderless Debate: A significant discussion took place regarding leader-based versus leaderless flooding reduction, focusing on operational complexity, blast radius, testing matrix, and transition strategies. There were concerns about the perceived complexity and inflexibility of leader-based approaches, while others raised concerns about the testing and risk associated with leaderless.
Reverse Prefix Metric Extension: Proposed a new extension to advertise reverse prefix metrics to address asymmetric routing scenarios where strict RPF checks fail. This was challenged as already available using FlexAlgo with a reversed metric and the value of this solution questioned for networks implementing FlexAlgo, but it was defended in the non-FlexAlgo world, particular with inter-area routes.
Load Balancing Alternate Paths: Proposed extensions to advertise link bandwidth utilization and enable the computation of load balancing alternate paths. The rapid updates required for link bandwidth information and the potential for network instability were raised as concerns. Similar solutions already exist through tactical traffic engineering (SRTE).
LSR YANG Modules: An update was provided on the progress of the LSR YANG modules, including plans for splitting the OSPF-based module and dependencies on the SRV6 YANG module in the SPRING working group. The chairs encouraged feedback from service providers on the level of detail included in the modules.
Energy Efficiency Flex-Algo: Discussed how to use Flex-Algo to avoid links and nodes with high-energy consumption. Raised question about how metrics about link and node topology tie to energy consumption with dynamic updates every 10 seconds.

Decisions and Action Items

Adoption Call for Leaderless Draft: Chairs will initiate an adoption call for the leaderless flooding reduction draft.
Reconcile TLV Definitions: Ensure consistent handling of algorithm and version advertisements across different drafts (Distop Flood and Flood Reduction Architecture).
Further Discussion of Load Balancing Alternate Paths: The presenter was asked to review the Tactical Traffic Engineering draft and continue the discussion on the mailing list.
Contact Spring WG Regarding SR6 Yang Module: To inquire about the status of the SR6 YANG module and offer assistance if needed.
Presenters to Review Comments and Update Drafts: All presenters to review comments and update drafts accordingly.

Next Steps

Adoption call of the leaderless flooding reduction draft
Mailing list discussions to further refine the leader-based vs. leaderless approaches, TLV encoding, and the potential benefits of load balancing alternate paths.
Presenters to update their drafts based on feedback received during the meeting and on the mailing list.