Session Date/Time: 24 Jul 2024 20:00

pim

Summary

This PIM working group meeting at IETF 120 covered several key topics, including updates on existing drafts, presentations of new drafts related to IGMP/MLD proxy enhancements, PFM enhancements, multicast addressing lessons learned, ZeroConf, and multicast application port handling. A significant portion of the meeting focused on a draft proposing multi-topology support in PIM, which sparked a lengthy debate about its necessity and design. The meeting concluded with updates on document status and calls for review.

Key Discussion Points

IGMP/MLD Router Alert Deprecation: Discussion about potential removal of router alert from MLDV2BIS and the importance of maintaining compliance with existing implementations.
IGMP/MLD Proxy Enhancements: Presentation of a draft introducing extensions to support multiple upstream interfaces for IGMP/MLD proxies, including subscriber-based and channel-based upstream interface selection mechanisms. The discussion focused on the use of Unicast routing information for interface selection and potential misconfigurations in shared link scenarios.
PFM Enhancements: Presentation of a merged draft combining forwarding enhancements and sub-TLV definitions for PFM. The flooding optimization using router ID announcement in PIM HELLOs and relaxed RPF checks was discussed.
Multicast Addressing Lessons Learned: Update on a draft documenting the history and evolution of multicast addressing, with a recent addition covering dynamic group address allocation. Suggestions were made to expand the section on addressing to include a broader story of addressing schemes and relevant protocols.
ZeroConf Updates: Presentation on recent discoveries and updates to the ZeroConf draft, including the introduction of a "veto record" to address collisions within switch hardware (hash table limitations).
Multicast Application Ports: Presentation of a proposal to reserve two ports for multicast applications, aiming to address port assignment scarcity. This sparked a detailed discussion about socket options (reuse adder, reuse port), filtering at the kernel level, and potential conflicts with Unicast applications and SSM.
Multi-Topology in PIM: Presentation and debate about a draft proposing extensions to support multi-topology and flex algorithm usage in PIM. The core argument revolved around whether PIM's inherent protocol independence and existing mechanisms (e.g., VRFs) already adequately address this requirement. Concerns were raised about the complexity of managing networks with different sources using different topologies and algorithms. The group discussed whether policy decisions are based on source of receiver.
LISP Multicast: Discussion of the status of LISP multicast documents and the need to standardize existing experimental RFCs. A list group mapping document was presented that addressed how to map a GEID to a GR-Loc
IGMPv1 Retirement: Update on the effort to retire IGMPv1 and revise RFC 1112. This includes removing the section that contains the IGMPv1 spec and adding more detail on IPv6 implementation.

Decisions and Action Items

IGMP/MLD Proxy Enhancements: The authors will consider the use of Unicast routing information for interface selection.
PFM Enhancements: Authors encouraged to prototype and gather ideas for sub-TLVs.
Multicast Addressing Lessons Learned: Authors to expand the section on addressing to include a broader history of addressing schemes.
ZeroConf Updates: Present ZeroConf to the APPS area.
Multicast Application Ports: Further investigation is needed into the API level interaction between different platforms.
Multi-Topology in PIM: The presenters will send the draft to the mailing list for further review.
IGMPv1 Retirement: Working Group Last Call for the draft.

Next Steps

Authors to address action items identified during the meeting.
Mailing list discussions to continue on the topics of MLDV2 router alert deprecation and multi-topology support in PIM.
Progress the IGMPv1 revision.
Working group to prepare for publication requests.