Re: [pim] [MBONED] IGMPv3 backward compatibility issue killing SSM

Hi Brian

I don't think changing defaults would be sufficient. My concern (and I
think that is what others are concerned about as well) is that hosts
and routers fall back to older versions when there is an older version
querier, as specified in 7.2.1 and 7.3.1. Regardless of the default,
it says that they must change mode or fall back.

I think we need some text where we RECOMMEND that hosts and routers
have a knob that disables compatibility mode and makes the host/router
always operate in IGMPv3 mode. This should of course be off by default
(fall back as usual). I'm happy if there is a more lightweight
approach that I'm not seeing.

Regards,
Stig

On Tue, Apr 2, 2024 at 12:10 PM Brian Haberman <brian@innovationslab.net> wrote:
>
> Hi Hitoshi,
>
> On 3/20/24 10:01 PM, Hitoshi Asaeda wrote:
> >
> > I thought what we need to clarify in DS IGMPv3/MLDv2 RFCs is that, as Brian mentioned, we can simply add recommended default settings for the compatibility mode variables. That’s all, I thought.
> >
> > But you remind me of the following four situations.
> >
> > 1. querier = SSM capable, forwarder = SSM capable -> no fallback
> > 2. querier = SSM capable, forwarder = non-SSM capable -> fallback
> > 3. querier = non-SSM capable, forwarder = SSM capable -> no fallback (and SSM capable router must become (replace) querier?)
> > 4. querier = non-SSM capable, forwarder = non-SSM capable -> fallback
> >
> > I wonder how above 2 and 3 are clearly considered in some RFCs?
>
> Which RFCs are you worried about? I think 3376 and 3376bis cover this in
> section 7.3 with discussion of the compatibility mode and group
> compatibility mode variables. We would augment that discussion with a
> recommendation that those compatibility mode variables default to IGMPv3
> mode.
>
> Table 9 in section 7.2.1 already indicates that hosts default to IGMPv3
> mode. We need to indicate a similar default in section 7.3.1.
>
> Regards,
> Brian
>
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