Subject: [rbridge] Consensus around MGROUP set of PDUs

From: Erik Nordmark <[email-masked]>
Date: Fri, 04 Jun 2010 09:38:47 -0700

Based on the recent discussion on the list, and not having found any
earlier discussion on the MGROUP set of PDUs on the TRILL WG mailing
list, it seems that there was never any TRILL WG discussion and
consensus about the need for or use of separate PDUs for multicast
membership.

The fact that there was some IS-IS WG discussion about this seems
unrelated, since the TRILL WG is the one to decide what they need from
IS-IS. And in the trill-protocol spec we don't specify any need for
additional PDU types for multicast.  In fact the document seems to talk
about TLVs and sub-TLVs in the regular LSP PDU:

4.2.4.4 TRILL LSP Information

    The information items in the TRILL IS-IS LSP that are mentioned
    elsewhere in this document are listed below. Unless an item is stated
    in the list below to be optional, it MUST be included. Other items
    MAY be included unless their inclusion is prohibited elsewhere in
    this document. The actual encoding of this information and the IS-IS
    Type or sub-Type values for any new IS-IS TLV or sub-TLV data
    elements are specified in a separate document [layer2].

Note that for the MTU testing in section 4.3.2 it is clear that the
expectation is that new IS-IS message types are needed.

Hence I conclude that the TRILL WG consensus has been to not require any 
new MGROUP PDU types.

If there is disagreement, or a need to revisit this, then I suggest the
proponents of MGROUP PDUs for TRILL make the case in the TRILL WG why
this would be required for TRILL's use of IS-IS. But that would be a
change from the current TRILL protocol specification.

    Erik

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From: Erik Nordmark <[email-masked]>
Date: Fri, 11 Jun 2010 08:46:39 -0700

> about TLVs and sub-TLVs in the regular LSP PDU:

The "unrelated" text above seems to have been too brief and as a result 
caused some confusion and concern.

It is in no means meant to disregard the work in the IS-IS working group 
or the layer2 draft. Those are all important and the participants in the 
TRILL working group should review that work, just like the participants 
in the IS-IS WG should review the IS-IS relevant parts of the TRILL 
specifications. To the extent you (as participants) feel you haven't 
done so, I do recommend that you review that work and comment on the 
IS-IS list.

My comment was merely in regards to my role as WG co-chair in 
determining TRILL WG consensus. Thus it would have been more appropriate 
to say:
	The fact that there was some IS-IS WG discussion about this
	seems unrelated to me as a co-chair determining TRILL WG
	consensus,

While that might seem unnecessarily process oriented, I think that if 
the individual WGs do not follow a process that makes the WG consensus 
clear, it gets even harder to do reasonable inter-WG and cross-IETF 
coordination.

Sorry for my unclear choice of words,
     Erik