[rbridge] When would an RBridge say "I don't want layer 2 multicast"?

[Joe Touch]

Donald Eastlake wrote:
> The Other Multicast bit was added after Dino Farinacci advocated it at
> the last Chicago meeting. (See minutes:
> http://www.ietf.org/proceedings/07jul/minutes/trill.txt) 

The minutes indicate a suggestion to put the bit in, but not a clear
reason why it's needed. The notes only indicate that this was a
"suggestion", then declare "consensus to be confirmed on the list.

The post you made on the email list in July indicates consensus at the
meeting, even though that wasn't indicated in the minutes:
http://www.postel.org/pipermail/rbridge/2007-July/002399.html

> This was put
> through a consensus call on the working group mailing list resulting
> in the formal consensus determination here:
> http://www.postel.org/pipermail/rbridge/2007-September/002470.html.

Besides your mail, there was only one post from James Carlson endorsing
the idea:
http://www.postel.org/pipermail/rbridge/2007-July/002400.html

Two months later you declare consensus based on "plenty of support and
almost no opposition". There was no discussion on the mailing list.
There was not really "plenty of support" on the mailing list.
http://www.postel.org/pipermail/rbridge/2007-September/002470.html

> This bit has been in the draft since verison -06. It defaults to "on"
> so, unless you go to some effort to configure it to off, all RBridges
> do get all the non-IP derived multicast traffic for the VLANs they
> advertise they are connected to. It doesn't have any effect on layer 2
> or TRILL control frames.

The question is "why do we need this complexity"? I appreciate it won't
cause problems if defaulted 'on', but having a bit means making sure
it's implemented and tested for vendors.

> In light of all this, I am very reluctant to consider changing this
> part of the design unless there is a clear consensus to re-open the
> issue.

Well, there's just as much consensus on the mailing list to open the
issue (my post) as there was to reach consensus to insert the bit in the
first place ;-)

Maybe what I'm asking is at least to clarify the issue. Is it really
needed as a bit, and if so, what is the impact of changing it from the
default value?

Joe