All things related to multicast

[John Zwiebel <>]

On Tuesday, May 14, 2002, at 11:36 AM, Toerless Eckert wrote:

> John, a host can not join to (*,G) and (S,G) with IGMPv3.
> Blame IGMPv3 to be a broken protocol, but basically you
> can either do an EXCLUDE({},G) membership (aka join (*,G))
> or an INCLUDE({S},G) (aka join (S,G)). Remember: IGMPv3
> allows you to only report INCLUDE or EXCLUDE mode for a group !

Just to be clear, I didn't mean to say that a host could
do this.  What I understand is that some routers, when
they get an include for an (S,G) that is not in the 232/8
range will send a PIM (S,G) join as you would expect, but
will -also- send a (*,G) join based solely on the IGMPv3
include.

Now, I might be mistaken (or rather my source might be mistaken).
IHNO on whether this is a "good thing" or a "bad thing".
Certainly, it would be something that should be considered by
the content provider and the receiver.


> Yes, with IGMPv3lite we can do this ;-))

IHNO on whether this is "good" or "bad".

> Cheers
>         Toerless
>
> Unless you come up with a completely twisted IGMP
> If a host does an IGMP
> On Tue, May 14, 2002 at 11:23:31AM -0700, John Zwiebel wrote:
> > Toerless Eckert wrote:
> > > On Tue, May 14, 2002 at 07:27:30AM -0400, Marshall Eubanks wrote:
> > > > I must admit that as a practical matter, I am dubious about the 
> > > > effacy of just
> > > > treating ASM sessions as if they were SSM. The two were deliberately 
> > > > intended
> > > > not to interoperate at the group level, and it seems like a kludge 
> > > > to treat them
> > > > as if they were.
> > > >
> > > > Marshall
> > >
> > > Please explain.
> >
> > FWIW:
> > I suggested to him that if the source was included in the
> > SAP description that a host could decide for itself
> > whether it wanted to join (*,G) or (S,G) allowing
> > him to use a single source to satisfy both SSM and ASM.
> >
> > Since some vendor implementations will have the last hop
> > join to the (*,G) as well as the (S,G) on receipt of
> > an IGMPv3 report, and for many other reasons, his
> > reluctance to follow this suggestion is valid.  I
> > totally agree that doing this is a kludge.
> >
> > But then so was MSDP, any-cast RP, and IGMP snooping.
> >
> > If the community wants to stay "virgin" and keep ssm
> > only in the 232/8 range (ie there is 'virgin SSM' and
> > 'compromised SSM' which would be to implement my
> > kludge.) that's fine with me.  There are probably
> > many reasons to do so.
> >
> > OTOH, there's no reason to not use the kludge.  It
> > doesn't result in any interoperability problems and
> > it does get packets to the receiver without having to
> > depend on MSDP.  So, I'm happy to leave it up to the
> > content provider and the receiver to make the
> > choice about whether or not they want to maintain
> > their virginity.
> >
> > z
>
> --
> Thanks
>    Toerless Eckert