++

Dear co-authors,

Your help with the following two issues in rfc9251 will be most appreciated:

Both issues refer to section 6.1 'Local IGMP/MLD membership Report 
Synchronization':

Firstly, I would like to propose a fix in a sub-section that describe the PE 
actions upon reception of a withdrawal of an IGMP Membership Report Synch route 
from another PE.
This sub-section has the following sentence: " If the DF no longer has the IGMP 
Membership Request (x,G) state for that BD on any ES for which it is the DF, it 
MUST withdraw its SMET route for that (x,G) group in that BD."
This sentence seems to ignore the possibility that the related PE may have also 
received an IGMP Report (x,G) message from an AC or PW VES that is connected to 
a single homed CE (for which case DF is not relevant), in which case this PE 
will still have an IGMP Membership Request (x,G) state, and therefore will 
still have to advertise the SMET Route for the related (x,G).
IMHO, this sentence shall be fixed to explicitly explain that the SMET Route 
shall be withdrawn ONLY if IGMP report (x,G) was NOT received from any MH or SH 
CE.

The second issue refers to the advertisement of SMET (x,G) route ONLY by the 
MH-ES DF upon the creation of IGMP Membership Request (x,G) state; In this RFC 
only the DF of the related multihomed ES advertises the (x,G) SMET Route. Which 
means that only the DF will receive the related (x,G) traffic (Assuming no 
other MH-ES mate PE has another AC/PW from which related IGMP Report (x,G) was 
received).
However, in case of failure of the related MH-ES AC on the DF or in case of 
failure of the PE that is elected as DF, we will have packet loss until he 
following procedures are completed:

  1.  DF election
  2.  The advertisement of SMET (x,G) Route by the newly elected DF
  3.  then wait for the remote PE, behind which the source resides, to process 
the above routes and send the traffic to the newly elected DF.
This might cause high traffic loss for the related (x,G) traffic.

I wander, can we assume that the related Multihomed Ethernet Segment BDF mate 
PE also advertise a related SMET route (x,G) and receive the related (x,G) 
traffic but forward it to the related AC when it becomes DF?  This might 
shorten the packet loss in case of DF failure quite significantly.

Looking forward to your response,

Nitsan Dolev
Ribbon Comunication

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