Group-to-RP Mapping AlgorithmPIM Working Group

Bharat Joshi

Infosys Technologies Ltd.

draft-joshi-pim-group-rp-mapping-00.txt

Need for a standard algorithm

• No existing RFC/Draft defines a complete algorithm.

• A standard algorithm is useful in interoperability.

• A standard algorithm can be used to predict the RP for a given Group

while running outside a router. This can be used for diagnosing PIM

protocol states.

Existing Algorithm

• PIM-SM has defined an algorithm which does not:

– Consider the origin of a Group-to-RP mapping and therefore treat all of them equally.

– Provide the flexibility that a specific statically created Group-to-RP mapping can override any dynamically learned mappings.

– Provide the flexibility to give higher priority to a specific PIM mode.

• PIM-STD-MIB has defined an algorithm that:

– Is not deterministic as it uses implementation-specific values.

– Can not be referenced by an implementation.

Proposed Algorithm• Select those Group-to-RP mappings that contains the Group address being

looked up.

• Select those mappings that are learned using 'static' configuration and are configured with 'override-dynamic' flag.

• Perform longest prefix match.

• Select mappings based on PIM Mode. PIM-BIDIR is preferred to PIM-SM.

• Select mappings based on origin of Group-to-RP mapping. Preference is 'bsr', 'auto-rp', 'embedded', 'static' and 'other'.

• Perform the Hash function.

• If there are still multiple mappings available, select the one that has higher IP address for RP address.

Next Step

• Review in WG mailing list.

• Working group item?