netdev - Re: Premature timeout for MLDv1 Host compatibility mode?

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Message-ID: <CAOLNa-cMkHaFxoWym-oVT6i7ZZ25tZPxaAEcwUuT1TB4kPGfag@mail.gmail.com>
Date:	Thu, 2 Aug 2012 16:03:24 +0200
From:	Dragos Ilie <dragos.ilie@...il.com>
To:	David Stevens <dlstevens@...ibm.com>
Cc:	netdev@...r.kernel.org, netdev-owner@...r.kernel.org
Subject: Re: Premature timeout for MLDv1 Host compatibility mode?

On Thu, Aug 2, 2012 at 3:57 PM, David Stevens <dlstevens@...ibm.com> wrote:
> Dragos Ilie <dragos.ilie@...il.com> wrote on 08/02/2012 09:28:49 AM:
>
>> MLDv1 packets do not have a QQIC field in the Query header. That is a
>> available for MLDv2 only. Consequently, MLDv1 queriers should fallback
>>  on the Query Interval variable, which has a  default value of 125
>> seconds. Since the Query Interval value is not user-configurable, I
>> assume that using the default value is a reasonable choice.
>
> The QQIC would come from v2 queries prior to the v1 query that
> triggered us to switch to v1. But, see below.

How about the scenario where you have only MLDv1 queriers? There will
be no prior v2 query

>
>> RFC 3810(MLDv2)  does mention that the Older Version Querier Present
>> Timeout must be calculated using the Query Interval from the last
>> received Query. I think the RFC is wrong on that point because I don't
>> see how a MLDv1 querier can convey its Query Interval to a listener.
>
> I'll look through this some more. I think using a fixed timeout
> is a bad idea since it doesn't account for shorter or longer interval
> queriers intentionally configured that way. Ideally it should,
> of course, be a positive indication that the v1 querier is gone
> based on v1 querier data (your point).
>
>                                                 +-DLS
>
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