Session Date/Time: 06 Nov 2023 08:30

LSR Meeting - IETF 118

Summary

The LSR working group meeting at IETF 118 covered a variety of topics related to OSPF and ISIS protocol extensions, including unreachable prefix advertisement, multi-part TLVs, YANG data models for implementation conformance statements (PICS), security property advertisement, database exchange procedures, and flexible algorithm enhancements. Several drafts were presented, and discussions focused on technical feasibility, backward compatibility, interoperability, and deployment considerations. Several requests for adoption were made.

Key Discussion Points

Unreachable Prefix Advertisement: Nikhil raised concerns about redundancy with existing mechanisms (overloading prefix origin) and the necessity of defining two flags (u-plan and up-plan). The chair emphasized the working group had already chosen a different approach for this specific use case.
Multi-Part TLVs: Less advocated for adoption, highlighting existing interoperable implementations and the inability to achieve backward compatibility. Chris and others voiced concerns about partial deployment and routing loops.
Yang Model for PICS: The presented model aims to describe implementation support for protocol features using YANG. Tony P emphasized the need for operator involvement to drive quality. AC questioned the granularity and scope of this effort. Chris suggested a way to indicate complete RFC support without deviations.
Advertising Link and Node Security Properties: Tony P introduced a framework for advertising security properties using the CIA model (Confidentiality, Integrity, Availability), with a focus on creating a taxonomy and enabling incremental deployment through flag usage.
Improved OSPF Database Exchange Procedure: Shaddha presented a solution to avoid traffic drops after router restarts. Leanne raised concerns about potential issues and requests for more data.
OSPF Adjacency Operation After Restart: Leanne compared two solutions for addressing the same problem (restart impacts) and argued for solution A based on reduced risk and better control. Les and Caitlyn advocated for merging the two drafts, citing complementary benefits and deployment advantages.
Advertising Unreachable Link in OSPF: Leanne presented an update focusing on using the maximum link metric to advertise unreachable links. This approach required introduction of a router capability to avoid routing loops with legacy implementations.
IGP Flexible Algorithm Resilient Class: Gao presented a proposal for enabling flexible algorithm path computation based on link loss. Discussion focused on the flapping problem with fluctuating loss values and the impact of Quality of Service on reported link loss.
OSPF Prefix Attribute Sub-TLVs: Wan presented a draft to introduce new prefix attribute sub-TLVs for OSPFv2 and OSPFv3, to address limitations with insufficient existing flags.
IGP Color-Aware Routing A novel attempt to enable Intent Aware Routing in IGP-only networks. It leverages existing and new constructs in IGP to distribute overlay paths. Concerns were raised about the scalability of the approach and reliance on ASBRs for inter-domain connectivity.

Decisions and Action Items

Multi-Part TLVs: Adoption call to be initiated.
OSPF Adjacency Operation After Restart: Shaddha and Leanne to discuss merging their respective drafts.
Unreachable Prefix Advertisement: This item has been technically addressed and a resolution has been identified.
Several topics: Community to contribute to the mailing lists in order to help guide decisions.

Next Steps

Authors to address feedback received during the meeting and on the mailing lists.
Continued discussion on the mailing lists for outstanding issues.
Potential follow-up sessions or interim meetings as needed.