RFC 4601, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", August 2006

Note: This RFC has been obsoleted by RFC 7761

Note: This RFC has been updated by RFC 5059, RFC 5796, RFC 6226

Errata ID: 1119
Status: Held for Document Update
Type: Technical
Publication Format(s) : TEXT
Reported By: Maren Peasley
Date Reported: 2007-12-21
Held for Document Update by: David Ward
Date Held: 2009-03-22

Section 4.5.1 says:

          The action "Send PruneEcho(*,*,RP)" is triggered when the
          router stops forwarding on an interface as a result of a
          prune.  A PruneEcho(*,*,RP) is simply a Prune(*,*,RP) message
          sent by the upstream router on a LAN with its own address in
          the Upstream Neighbor Address field.  Its purpose is to add
          additional reliability so that if a Prune that should have
          been overridden by another router is lost locally on the LAN,
          then the PruneEcho may be received and cause the override to
          happen.  A PruneEcho(*,*,RP) need not be sent on an interface
          that contains only a single PIM neighbor during the time this
          state machine was in Prune-Pending state.

Notes:

Forged PruneEcho messages could operate as a form of Denial-of-Service (effectively the same as a Prune(*,*,RP) in this context). The issue is resolved by using AH, but it is not listed as one of the forged message types in section 6.1.1.

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