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

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Date:	Thu, 2 Aug 2012 09:57:57 -0400
From:	David Stevens <dlstevens@...ibm.com>
To:	Dragos Ilie <dragos.ilie@...il.com>
Cc:	netdev@...r.kernel.org, netdev-owner@...r.kernel.org
Subject: Re: Premature timeout for MLDv1 Host compatibility mode?

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.

> 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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