Subject: Re: WG Last Call: IGMP Version 3 to Proposed Standard

From: Bill Fenner <[email-masked]>
Date: Fri, 14 Jul 2000 09:51:25 -0700

>I personally have not had the time to give this much thought although it
>does appear on the surface (at least it does to me) that IGMPv3 will have a
>*significant* impact on switches that are doing IGMP Snooping.

At a minimum, switches will need to be modified to recognize IGMPv3
reports.  This may actually be easier in IGMPv3 since the reports are
all sent to the same group address.

You can't do IP source filtering at the ethernet layer, so switches can
treat both source inclusion and exclusion reports as group joins, and
the "include none" as leaves.  (Does current IGMP snooping technology
do fast leave?)

  Bill

---

From: Bill Fenner <[email-masked]>
Date: Wed, 19 Jul 2000 10:27:50 -0700

>	so, instead of having this 'bit' or field indicate 'SPT' or shared
>tree [which is multicast routing knowledge], we can have it specify some
>kind of quality indicator [like low delay, or low overhead, for
>example]. This would then be translated by the router according to the
>multicast routing and the quality that can be provided.

Perhaps I'm missing something -- if so, I apologize.  But if you give
people a knob that says "Worse .. .. .. Better", they are likely to
just turn it towards "Better" (especially if there are no disincentives
to doing so, e.g. having to pay for it).  I'd much rather see all
routers just assuming that all hosts want good quality, rather than
see mechanism added to the spec which would probably eventually go
unused.

  Bill