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