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Bidirectional Protocol Independent Multicast (BIDIR-PIM)
RFC 5015

Document type: RFC - Proposed Standard (October 2007; Errata)
Document stream: IETF
Last updated: 2013-10-24
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 5015 (Proposed Standard)
Responsible AD: Bill Fenner
Send notices to: pim-chairs@tools.ietf.org

Network Working Group                                         M. Handley
Request for Comments: 5015                                           UCL
Category: Standards Track                                    I. Kouvelas
                                                             T. Speakman
                                                                   Cisco
                                                             L. Vicisano
                                                        Digital Fountain
                                                            October 2007

        Bidirectional Protocol Independent Multicast (BIDIR-PIM)

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   This document discusses Bidirectional PIM (BIDIR-PIM), a variant of
   PIM Sparse-Mode that builds bidirectional shared trees connecting
   multicast sources and receivers.  Bidirectional trees are built using
   a fail-safe Designated Forwarder (DF) election mechanism operating on
   each link of a multicast topology.  With the assistance of the DF,
   multicast data is natively forwarded from sources to the Rendezvous-
   Point (RP) and hence along the shared tree to receivers without
   requiring source-specific state.  The DF election takes place at RP
   discovery time and provides the route to the RP, thus eliminating the
   requirement for data-driven protocol events.

Handley, et al.             Standards Track                     [Page 1]
RFC 5015                   Bidirectional PIM                October 2007

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................4
      2.1. Definitions ................................................4
      2.2. Pseudocode Notation ........................................6
   3. Protocol Specification ..........................................6
      3.1. BIDIR-PIM Protocol State ...................................7
           3.1.1. General Purpose State ...............................8
           3.1.2. RPA State ...........................................8
           3.1.3. Group State .........................................9
           3.1.4. State Summarization Macros .........................10
      3.2. PIM Neighbor Discovery ....................................11
      3.3. Data Packet Forwarding Rules ..............................11
           3.3.1. Upstream Forwarding at RP ..........................12
           3.3.2. Source-Only Branches ...............................12
           3.3.3. Directly Connected Sources .........................13
      3.4. PIM Join/Prune Messages ...................................13
           3.4.1. Receiving (*,G) Join/Prune Messages ................13
           3.4.2. Sending Join/Prune Messages ........................16
      3.5. Designated Forwarder (DF) Election ........................18
           3.5.1. DF Requirements ....................................18
           3.5.2. DF Election Description ............................19
                  3.5.2.1. Bootstrap Election ........................20
                  3.5.2.2. Loser Metric Changes ......................20
                  3.5.2.3. Winner Metric Changes .....................21
                  3.5.2.4. Winner Loses Path .........................22
                  3.5.2.5. Late Router Starting Up ...................22
                  3.5.2.6. Winner Dies ...............................22
           3.5.3. Election Protocol Specification ....................22
                  3.5.3.1. Election State ............................22
                  3.5.3.2. Election Messages .........................23
                  3.5.3.3. Election Events ...........................24
                  3.5.3.4. Election Actions ..........................25
                  3.5.3.5. Election State Transitions ................26
           3.5.4. Election Reliability Enhancements ..................30
           3.5.5. Missing Pass .......................................30
           3.5.6. Periodic Winner Announcement .......................30
      3.6. Timers, Counters, and Constants ...........................31
      3.7. BIDIR-PIM Packet Formats ..................................34
           3.7.1. DF Election Packet Formats .........................34
           3.7.2. Backoff Message ....................................36
           3.7.3. Pass Message .......................................36

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