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Group-to-RP Mapping

Group-to-RP Mapping. IETF Draft: draft-ietf-pim-group-rp-mapping-00 Authors: Andy Kessler, Cisco Systems Bharat Joshi, Infosys Technologies Ltd. David McWalter, Data Connection Ltd. Need for Standard Algorithm. Need for standard deterministic algorithm

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Group-to-RP Mapping

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  1. Group-to-RP Mapping IETF Draft: draft-ietf-pim-group-rp-mapping-00 Authors: Andy Kessler, Cisco Systems Bharat Joshi, Infosys Technologies Ltd. David McWalter, Data Connection Ltd

  2. Need for Standard Algorithm Need for standard deterministic algorithm • No existing RFC/Draft defines a complete algorithm • A standard algorithm is required for interop • Resolves cases in which there are several group mappings for a single group from different sources • A standard algorithm could be used to determine the selected RP by an independent network management system

  3. What is new in this Rev ? • Hash function is removed from Algorithm • RFC 4601 and RFC 5059 suggested use of hash function is removed – discussed on PIM list and was agreed • New Section – Clarification of MIB Objects • Clarifies support for SSM and DM in group mapping table • New Use Case – Network Mgmt Systems • Algorithm explicitly deals with SSM and DM Group types • Draft now states that new algorithm deprecates group-rp-mapping algorithm in RFC 4601 and RFC 5060

  4. Clarification of MIB Objects Support for all multicast group ranges • It is acceptable to represent SSM and DM groups in the pimGroupMappingTable in the PIM-STD MIB • SSM and DM entries would have an RP with an address type of ‘unknown’ and a PIM mode of Dense Mode or SSM • Creates one stop shopping for all multicast group mappings • - Useful for NMS apps

  5. Use Cases • Default static Group-to-RP mappings with dynamically learned entries • Default infrastructure for general purpose apps and specific mappings for special apps that change more often • Static Group-to-RP mappings with override-dynamic flag • Network Operators need to ability to nail down the RP mappings statically and ignore all dynamic messages • Migration situations • After acquisitions or mergers companies will need deterministic method to move from one RP mapping method to another (e.g. AutoRP to BSR) • Use by Management Systems • Ability for NMS to determine Group-RP-Mappings used by a router

  6. Proposed Algorithm The RP would be selected with this preference: • Embedded RP • Static with 'override-dynamic' flag • Longest match • PIM-Bidir over PIM-SM • Origin preference - bsr, auto-rp, static and other • Highest IP address

  7. Current Issues with Draft • Minor Typos • ?

  8. References • Section 1.1 of RFC 5059 - BSR Mechanism for PIM • ... the router chooses only one of the RPs by applying a deterministic algorithm so that all routers in the domain make the same choice. It is important to note that this algorithm is part of the specification of the individual routing protocols (and may differ among them), not of the BSR specification. • Section 3.3 of RFC 5059 - BSR Mechanism for PIM • If the BSR learns of both BIDIR and PIM-SM Candidate-RPs for the same group range, the BSR MUST only include RPs for one of the protocols in the BSMs. The default behavior SHOULD be to prefer BIDIR.

  9. References • Section 4.7.1 of RFC 4601 - PIM-SM Protocol Spec • Describes the existing algorithm for choosing a group from multiple Group-to-RP Mapping. It does not address these issues • Does not consider the origin of a group-to-rp mapping (e.g. bsr, autorp, static, etc) • Allow for static override • Doesn't allow for higher priority of PIM-Bidir over PIM-SM • Section 4.7.2 of RFC 4601 - PIM-SM Protocol Spec • Describes the Hash function and talks about the highest IP address but only after the hash function.

  10. References • Section 7.1 of RFC 3956 - Embedded RP for IPv6 • To avoid loops and inconsistencies, for addresses in the range FF70::/12, the Embedded-RP mapping MUST be considered the longest possible match and higher priority than any other mechanism.

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