Session Date/Time: 28 Jul 2023 16:30

pim

Summary

The PIM working group meeting at IETF 117 covered several draft documents related to multicast protocols. Discussions included lessons learned from multicast deployments, updates to unicast-based PIM YANG models, extensions to PIM flooding mechanisms, a proposal to update RFC 1112 (Host Extensions for IP Multicasting), and zero-configuration multicast address assignment, along with a demonstration of a novel decentralized group allocation protocol (GAAP).

Key Discussion Points

Lessons Learned from Multicast Deployments: The draft aims to document the history and evolution of multicast protocols, including DDVRP, IGMP, and MSDP. Participants suggested including additional historical context, such as expired drafts related to problem statements.
Unicast-based PIM YANG Model Update: Updates to the YANG model draft include changes to support both IPv4 and IPv6 multicast group addresses, along with alignment of response times with existing MLD YANG models. A question arose about the document's relevance to the BEST working group, leading to a discussion about potentially re-adopting the draft in PIM if a response from BEST is not received.
PIM Flooding Mechanism Extensions: A proposal to extend PIM flooding mechanisms to include additional data about flows (e.g., bandwidth) was discussed. Concerns were raised about the complexity of adding extensive metadata, with suggestions to consider leveraging existing mechanisms like SAP and JSON encoding.
RFC 1112 Update: This update aims to remove IGMPv1 from RFC 1112 while retaining the rest of the IP multicast host stack specification. The discussion centered on maintaining backward compatibility for existing IGMPv2 and v3 implementations.
Zero-Configuration Multicast Address Assignment: Two proposals were presented: one focused on extending existing protocols (mDNS) primarily for Layer 2 applications and another based on a new decentralized protocol (GAAP). Concerns were raised about the applicability of these solutions for larger overlay networks.
GAAP Demonstration: A live demonstration of the GAAP protocol running over a LISP overlay, including satellite links and NAT traversal, showcased the feasibility of decentralized multicast group allocation in complex network environments.
Adaptive Stability Multicast: A presentation on adaptive stability multicast was discussed. This complex method was for improving the efficiency of multicast trees in lossy networks. Several concerns were raised about the complexity of the implementation and data in the packet.

Decisions and Action Items

Adopt Zero Comp problem statement draft: The chair will start an adoption call on the mailing list.
Adopt draft-ietf-pim-1112bis: The chair will start an adoption call on the mailing list.
Unicast-based PIM YANG Model Update: If no response is received from the BEST working group, consider issuing an adoption call in the PIM working group.
PIM Flooding Mechanism Extensions: The author will consider suggestions for incorporating SAP principles and alternative data encoding formats (JSON).
Adaptive Stability Multicast: The authors will address concerns about complexity.

Next Steps

Send adoption call for "Zero Comp problem statement draft" to the mailing list
Send adoption call for "draft-ietf-pim-1112bis" to the mailing list
Continue discussions on the mailing list to refine the remaining drafts.
Authors to address comments raised during the meeting and on the mailing list.