Igmp Group-Source specific Retransmission

Hi All,

I was going through the IGMPv3 RFC 3376  and was not clear on the below
Mentioned section.

/*---------------------------------------------------------------------------------------------------------*/
6.6.3.2. Building and Sending Group and Source Specific Queries

   When a table action "Send Q(G,X)" is encountered by a querier in the
   table in section 6.4.2, the following actions must be performed for
   each of the sources in X of group G, with source timer larger than
   LMQT:

   o Set number of retransmissions for each source to [Last Member Query
     Count].

   o Lower source timer to LMQT.

   The router must then immediately send a group and source specific
   query as well as schedule [Last Member Query Count - 1] query
   retransmissions to be sent every [Last Member Query Interval] over
   [Last Member Query Time].  The contents of these queries are
   calculated as follows.
/*-----------------------------------------------------------------*/


This section talks about how the group-source specific queries are build and
Send out.

Suppose our robustness variable is set to 2(default value).
And Last Member Query Interval is 10 Sec.

Any group-source specific query need to be transmitted robustness number of times
That is 2 times in our case and separated by LMQI which 10 sec.
So 2 queries has to be sent across Last Member Query Time which is 20 sec.


Now suppose we already sent Q(G,X) query for a group at T1 with set of sources. And we received
A report which causes new Q(G,(X+Y)) needs to be sent and T2( before T1+LMQI). Where Y is new set of sources to be
Queried. New Query will be sent with all sources merged from previous and new(x + y).

So the sources x already two queries will be sent and not separated by LMQI in this scenario.

My question is whether we need to send one more query after LMQI ( at T1+LMQI) for x
Set of sources for this group?

If we need to then we will be sending 3 queries for x set of sources as follows.

Time interval T1
Time interval T2
Time interval T1+LMQI

Which is not correct.

Let me know whether we should send query for x set of sources for this group
At T1+LMQI interval.

Thanks and Regards
Deepak

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