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

[Stig Venaas <[e-mail]>]

Hi Brian

This looks great to me, but I would like to hear from people that
raise this issue to see if they are OK.
Toerless, Lenny, Nick, Hitoshi (and others), does this look good to
you? Can we proceed with the publication?

Thanks,
Stig


On Tue, Apr 16, 2024 at 5:31 AM Brian Haberman <[e-mail]> wrote:
>
> Hi Stig,
>       Thanks for the clarification...
>
> I am curious if the following two additions would address this issue
> without delaying the advancement of the documents to Internet Standard.
>
> 1. In Section 7.2.1 - Add this to the last paragraph : "It is
> recommended that implementers provide a configuration option to disable
> use of Host Compatibility Mode to allow networks to operate only in SSM
> mode. This configuration option should be disabled by default."
>
> 2. In Section 7.3.1 - Add an additional bullet : "It is recommended that
> implementers provide a configuration option to disable use of
> compatibility mode to allow networks to operate only in SSM mode. This
> configuration option should be disabled by default."
>
> Regards,
> Brian
>
> On 4/8/24 5:26 PM, Stig Venaas wrote:
> > 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 <[e-mail]> 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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