RFC 4601, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", August 2006
Note: This RFC has been obsoleted by RFC 7761Source of RFC: pim (rtg)
Errata ID: 1135
Status: Held for Document Update
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
Sections 6.4 and A.2
The rationale for this is that there is no way in PIM-SM to prune traffic off the (*,*,RP) tree, except by Joining the (*,G) tree and then pruning each source individually.
The paragraph beginning “The rationale for this…” describes a condition where a small cause can have a great effect – a (*,*,RP) join could cause state that, if it is not needed, requires a (*,G) join and many prunes for each source. This is mentioned as the last point in section 6.4, but section 6.4 fails to mention that “undoing” this state requires a join followed by multiple prunes.