Subject: Differences in query retransmission scheduling between IGMP v2 & v3

From: Mladen Sablic <[email-masked]>
Date: Fri, 22 Jun 2001 15:46:58 +0100

Hi all,

I was looking at "6.6.3 Building and Sending Specific Queries"
in draft-ietf-idmr-igmp-v3-07.txt and I see that the scheduling
of queries and lowering of expiry time has changed with respect
to [Last Member Query Interval] or LMQI.

In IGMPv2 RFC 2236 section 6:

- Group timer is lowered to LMQI*[Last Member Query Count].

- Queries were retransmitted separated by LMQI
  with Max Response Time of LMQI.

This implies that if reports from all but the last query were lost
then the last report would still arrive before group timer expires.

The logic behind 6.6.3 is that the Max Resp Time in queries must
be set to some value other than LMQI even tough this is nowhere
explicitly mentioned.

If the Max Resp Code is set with Max Resp Time = LMQI the response
from retransmitted queries could possibly not arrive before group
or source timer expires.

Does this mean that Max Resp Time should be set to:
LMQI/[Last Member Query Count]?

Is this correct or am I missing something?

Thanks,

Mladen

<[email-masked]>