PIM%20MT-ID%20Join%20Attribute

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PIM MT-ID Join Attribute

• draft-cai-pim-mtid-00
• IETF 73, Minneapolis

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Objective

• Build non-overlapping multicast forwarding trees
• Improve resilience of multicast applications
• Support divergent trees even if sources are the
  same

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Approach

• Create multiple topologies for RPF
• Routes from MT capable unicast routing protocols
  or via import policies
• Choose a topology based on
• Configuration
• PIM MT-ID Join-Attribute from downstream
• Send PIM MT-ID to upstream in Join, or downstream
  in Assert

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Attribute Definition

• Forward Bit 1
• Type 3
• Length 2
• Value 1-65535

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Key Design Decisions

• No new PIM Hello Options
• For Join and Asserts only
• Minimum required for SSM
• Configuration on last hop router always needed
• Configuration on RP and first hop DR for SM
• Configuration on Bidir Upstream

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Key Design Decisions (contd)

• MT-ID 0 is not encoded
• Not including MT-ID not considered a conflict
• For incremental deployment
• Forward Bit
• Since every router may ignore the MT-ID in Join
  packets, does Forward Bit need to be 1?

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Key Design Decisions (contd)

• Conflict resolution, upstream router
• Conflicting MT-ID from downstream neighbour
  resolved using draft-ietf-pim-join-attributes
• MT-ID not used to decide the Assert winner

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Key Design Decisions (contd)

• Conflict resolution, downstream router
• Join suppression if a router (with a lower IP
  address on the LAN) sees a Join from another
  downstream router with a different MT-ID, it
  suppresses its Join (RFC4601)
• Or not, by following draft-ietf-pim-join-attribute
  s?
• If Assert winner uses different MT-ID, Assert
  winner becomes the RPF neighbour, but MT-ID is
  not encoded in Joins

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Next Step

• WG comments welcome
• Consensus on key design decision validation of
  attribute, conflict resolution rules etc
• WG document
• By San Francisco, if no major issues?