draft-ietf-l3vpn-2547bis-mcast-bgp section 13

["HEMIGE Venu" <[e-mail]>]

I think the specification in section 13 needs some enhancement.
Otherwise, there are cases where it would not work.
 
1. Section 13.2: This sections says that if an egress PE has (C-*,C-G)
states and it has "one or more" source-active routes, then it must pick
"one of them" and setup a (C-S,C-G) forwarding state to accept traffic
for that (C-S,C-G) from the originator of that source-active route. If
all PEs select a single upstream PE for an (C-S,C-G), there should be
only one source-active route available. I suppose more than one is
possible when you have a PE configured as RP and hence it sends source
active routes into the MVPN cloud. Is that correct?
 
2. Section 13.2: If the above assumption is correct, then I think it is
wrong to say that the egress PE must pick one of the source-active
routes and setup forwarding state to accept traffic from the
"originator" of that source-active route. It is possible that the
orignator may not be in the path to C-S. Even if it is, it would break
the "single upstream PE" rule. I think the RPF tunnel should be the one
from the single forwarder PE regardless of where the Soure-Active is
received from. Section 14 says this but Section 13 does not.
 
3. Section 13.2: I think it is insufficient to say that the egress PE
creates just the forwarding state for (C-S,C-G). I think the egress PE
MUST send a Source Join Route to explicitly join the (C-S, C-G) tree.
Here is why: It could be that the only reason for the Source Join Route
and hence the Source-Active in the MVPN is because C-RP sent it after
C-S sends PIM registers to C-RP. As per section 13.2.1, the upstream PE
for the (C-*,C-G) creates a (C-S,C-G,rpt) prune state and sends this
prune to the RP when it receives a Source Active. As a result, C-RP
would prune itself off the (C-S,C-G) tree and this would result in the
Source Join and Source-Active routes from getting withdrawn from the
MVPN. This would result in a repetitious cycle of Source Join,
Source-Active, S,G,Rpt prune, Withdraw Source-Join, Withdraw
Source-Active, S,G,Rpt join, ...
 
The best way to fix these issus is to require that all egress PEs that
have (C-*,C-G) states MUST send Source Join Routes when they receive a
Source-Active. 
 
Please let me know if I am missing something.
 
Thanks,
-Venu