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: 1121
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
Section 4.5.4 says:
Prune-Pending (PP) The router has received a Prune(S,G,rpt) on this interface from a downstream neighbor and is waiting to see whether the prune will be overridden by another downstream router. For forwarding purposes, the Prune-Pending state functions exactly like the NoInfo state.
If a single Prune(S,G,rpt) stops forwarding, then traffic can be interrupted even when it is still needed. There is a random delay between 0 and Effective_Override_Interval(I) (0 – 2.5 seconds by specification defaults) in which traffic stops until it is overridden and traffic starts flowing again. This appears to be an optimization for efficiency vs. reliability. I believe that this should be noted and made into an optional optimization.