Subject: [magma] Non-Querier behaviour on receiving grp specific or grp-and-src specific queries

From: "Suvendu Mozumdar" <[email-masked]>
Date: Fri, 23 May 2008 01:25:57 -0700

Hi,

     I have an issue for which the RFC 3376 does not suggest anything.
Lets say in a Lan there are two igmpv3 routers and one igmpv3 host
present. Lets say Q1 is querier and Q2 is non-querier. Now Host1 sends
include s1 for grp G1. Both Q1 and Q2 will have an entry in their
respective database. Now Host1 sends a report block s1 for grp G1. Q1 on
receipt of this block report will start LMQT timer, set the source timer
of s1 to LMQT and start sending group and source specific queries for
G1/s1. After LMQT expires Q1 will delete the entry of G1/s1 from its
database. Now what will be the non-querier's behaviour. Will it also
start LMQT, in that case Querier's LMQT and non-querier's LMQT (which is
LMQC*LMQI) may differ based on different LMQC values. Non-querier comes
to know about the querier's LMQI from the Max Response Code in the
specific query pkt but what about querier's LMQC, non-querier has no way
to know about the querier's LMQI.

Can anyone throw some light on this?

Thanks

Suvendu.

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From: Bharat Joshi <[email-masked]>
Date: Fri, 23 May 2008 14:07:00 +0530

Suvendu,

> respective database. Now Host1 sends a report block s1 for grp G1. Q1
> on receipt of this block report will start LMQT timer, set the source
> timer of s1 to LMQT and start sending group and source specific
> queries for G1/s1. After LMQT expires Q1 will delete the entry of
> G1/s1 from its database. Now what will be the non-querier's behaviour.
> Will it also start LMQT, 

Please look at section 6.6.1. When a non-querier receives a query, it
reduces its corresponding timer to LMQT which can be derived from
max-response code.

> in that case Querier's LMQT and non-querier's LMQT (which is
> LMQC*LMQI) may differ based on different LMQC values. Non-querier
> comes to know about the querier's LMQI from the Max Response Code in
> the specific query pkt but what about querier's LMQC, non-querier has
> no way to know about the querier's LMQI.

Non-querier does not need to know LMQC as it is not required. LMQC is
required for a querier to generate number of queries.

Also most of the times, it is expected that all routers are configured
with same values but things should still work if they are not.

Hope this helps.

Thanks,
Bharat

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From: "Suvendu Mozumdar" <[email-masked]>
Date: Sun, 25 May 2008 22:17:46 -0700

Hi Bharat, please see inline :

-----Original Message-----
From: Bharat Joshi [mailto:[email-masked]] 
Sent: Friday, May 23, 2008 2:07 PM
To: Suvendu Mozumdar
Cc: [email-masked]
Subject: Re: [magma] Non-Querier behaviour on receiving grp specific
orgrp-and-src specific queries

Suvendu,

Please look at section 6.6.1. When a non-querier receives a query, it
reduces its corresponding timer to LMQT which can be derived from
max-response code.
Suvendu : As per section 8.10, LMQT = LMQC*LMQI, I agree that LMQI is
the max-response code in the specific query, but LMQC is configurable
and MAY differ in querier and non-querier. That's where my doubt arises.

Non-querier does not need to know LMQC as it is not required. LMQC is
required for a querier to generate number of queries.
Suvendu : Not only that, LMQC is used in calculating LMQT, pl refer
section 8.10.

Hope this helps.

Thanks,
Bharat

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has taken 
every reasonable precaution to minimize this risk, but is not liable for
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From: Bharat Joshi <[email-masked]>
Date: Mon, 26 May 2008 19:59:22 +0530

Hi Suvendu,

> and MAY differ in querier and non-querier. That's where my doubt arises.

Non-querier need not use LMQT in turn LMQC at all. They can simply lower down their group/source timer to LMQI calculated based on Max-Response-Code and they do it for each group/group-source specific query.

> Suvendu : Not only that, LMQC is used in calculating LMQT, pl refer

Please see above.

Thanks,
Bharat