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

[Brian Haberman <[e-mail]>]

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