Session Date/Time: 26 Jul 2022 14:00

pim

Summary

The PIM working group held its second physical meeting at IETF 114. The session covered status updates on several drafts, including those in the RFC Editor's queue and those recently adopted or nearing working group last call. Key discussions revolved around the adoption of PIM Light, the requirements for multicast address allocation in zero-configuration marine networks, and the advancement of IGMPv3 and MLDv2 to Full Standard, specifically addressing the incorporation of SSM extensions. The meeting concluded with feedback on a proposal for PIM Static Multicast Routes.

Key Discussion Points

Working Group Document Status:
- PIM YANG Model: Remains in RFC Editor's queue, pending publication of dependent documents, particularly the updated BFD model (RFC 9127bis), which is currently in AUTH48.
- IGMP/MLD Extension Draft: In RFC Editor's queue, currently in AUTH48, expected to be published soon.
- DR Drafts (Improvement and Backup DR): Authors will work on updates. The working group needs to determine if both explicit and non-explicit signaling solutions for DR behavior are required or if one approach should be standardized. Community review and feedback are requested.
- IGMP/MLD Proxy YANG Model, PIM Register Packing, PIM Join/Prune Packing: Publication requested for these drafts.
- SR Point-to-Multipoint Policy: A poll was conducted to assess readiness for Working Group Last Call. Discussions involved coordinating with the SPRING working group regarding a related replication segment draft.
- LISP Extensions: No significant progress, authors urged to update.
- PIM Point-to-Multipoint Policy Ping: Awaiting feedback from the MPLS group and IANA sub-TLV assignment.
- PIM MLFR based on TI-LFA (TILFA): Recently adopted.
PIM MLFR based on TI-LFA (TILFA) Presentation:
- Presented by Isung Liu (China Mobile), introducing a new mechanism for PIM MFR using TI-LFA without additional PIM protocol extensions.
- Highlighted limitations of RFA/Remote RFA due to topology dependence, which TI-LFA aims to overcome by providing 100% network protection.
- Proposed using Node-SID as RPF vector (type 0) or Adjacency-SID as explicit RPF vector (type 4) for backup tree establishment.
- Next steps include adding details for SR-MPLS and SRv6 networks.
PIM Light Draft Discussion:
- Presented by Stig Venaas and Mahesh Jethanandani, seeking working group adoption.
- Motivated by the need to signal multicast states between disjoint PIM domains without establishing PIM adjacencies (e.g., PIM over BEER).
- Updates in V2 included removing Assert messages and discussing security considerations for automatic PIM Light interface configuration.
- Feedback included considering the implications for BSR message forwarding and clarifying Hello message processing.
Multicast Address Allocation for Zero Configuration Networks (NMA) Presentation:
- Nate Carroll (Garmin/NMEA) presented on challenges in self-contained marine networks (Onenet) requiring dynamic multicast address allocation for zero-configuration deployments.
- Problem: Coexistence of devices with varying link speeds and the potential for MAC address collisions when using link-scoped IPv6 multicast addresses, as switch hardware often only filters on the destination MAC address (lower 32 bits of IPv6 Group ID) rather than the full IPv6 address or source.
- Considered solutions like SSM (hardware limitations), MADCAP (central server, single point of failure), and ZMAAP (expired draft, incomplete).
- Discussion explored the necessity of dynamic allocation versus static provisioning, hashing-based allocation for collision avoidance, and the trade-offs between protocol complexity and ease of deployment for non-expert users.
- Consensus leaned towards defining a clear set of requirements before proposing a specific protocol solution.
IGMPv3 and MLDv2 to Full Standard (RFC 3376bis and 3810bis) Update:
- Brian Haberman presented on advancing these RFCs to Full Standard.
- Key Issue: RFC 4604 (SSM for IGMPv3/MLDv2) formally updates these RFCs but is currently a Proposed Standard.
- Proposed Solution: Incorporate the protocol changes from RFC 4604 directly into the biz documents, which would then obsolete RFC 4604. This implies RFC 4604 is also ready for Full Standard advancement.
- Process concerns were raised regarding justifying the "significant changes" from RFC 4604 as existing updates when moving to Full Standard, and the need for a shepherd.
PIM Static Multicast Routes Presentation:
- Authors were not present, co-chair summarized their proposal to standardize static multicast routes with forwarding locations and redistribution options.
- Discussion questioned the necessity of standardizing functionality already widely implemented via CLI commands in various vendor equipment, and whether this is a better fit for a YANG model or the MBONDI (Multicast Operations) group.
- Concerns were raised about the complexity of specifying redistribution mechanisms and potential for network issues.

Decisions and Action Items

SR Point-to-Multipoint Policy:
- Decision: Proceed with initiating a Working Group Last Call.
- Action: Chairs to consult with SPRING working group chairs regarding the related replication segment draft. The mailing list will be used to gather feedback on readiness.
PIM Light:
- Decision: Initiate an adoption call on the mailing list.
- Action: Sandy (acting chair for this draft) to send the adoption call email. Authors to consider feedback regarding BSR message handling, security configurations, and Hello message processing.
IGMPv3 and MLDv2 to Full Standard (RFC 3376bis and 3810bis):
- Decision: Incorporate the protocol changes from RFC 4604 into the RFC 3376bis and 3810bis documents.
- Action: Brian Haberman to send a mailing list message explicitly asking for feedback on this incorporation approach. A shepherd needs to be identified to manage the process and provide justification for the IESG regarding the consolidation of RFC 4604's updates.
PIM Static Multicast Routes:
- Action: Chairs to inform the authors of the feedback received, suggesting they engage on the mailing list and potentially consult with the MBONDI working group. No immediate standardization action from PIM WG.

Next Steps

DR Drafts: Authors to continue work, incorporating feedback, to facilitate a working group decision on the solution approach (explicit vs. non-explicit signaling).
PIM MLFR based on TI-LFA (TILFA): Authors to add more detailed information regarding SR-MPLS and SRv6 networks to the draft and solicit further working group feedback.
NMEA Multicast Address Allocation: Nate Carroll to develop a requirements document for zero-configuration multicast address allocation in marine networks, outlining deployment workflows and use cases, before proposing specific technical solutions.
General: All working group participants are strongly encouraged to read the drafts under discussion and provide constructive feedback on the mailing list to ensure robust and well-vetted solutions.