Subject: RE: uni-based-mcast and malloc-ipv6-guide

From: "Dave Thaler" <[email-masked]>
Date: Tue, 18 Sep 2001 11:05:32 -0700

> -----Original Message-----
> From: Dave Thaler
> Sent: Tuesday, September 18, 2001 10:22 AM
> To: Erik Nordmark
> Cc: [email-masked]; [email-masked]
> Subject: RE: uni-based-mcast and malloc-ipv6-guide
> 
> Erik Nordmark asks:
> > I fail to understand why routing might fail. Could you explain?
> > I do understand that there is a different probability of allocating
> > duplicate
> > uni-based mcast addresses should the unicast prefix be assigned to
> another
> > entity, but this doesn't lead to routing failing unless you are
> assuming
> > that routing will do something it doesn't currently do.
> 
> Just like providers do source ingress filtering, there might be
> something similar that providers would do here.  (Maybe, maybe not.)

Another example would be if uni-based mcast prefixes are used
with BGMP, or any other scheme, to locate the root (domain) of the 
multicast tree without doing anything different in BGP.  If the 
domain loses its old unicast prefix, after which it's advertised 
by no one, then the derived multicast addresses would similarly
be (intentionally) unusable inter-domain.

-Dave

---

From: Erik Nordmark <[email-masked]>
Date: Wed, 19 Sep 2001 11:44:08 +0200 (CEST)

> be (intentionally) unusable inter-domain.

Dave,

If so it would be a fine thing to explicitly document this in the draft
as a potential issue.

One of my comments/questions in the first mail (which you passed to Brian
as an editorial one) was the issue of what aspects of the IPv4 stuff we
need and need not carry forward to IPv6.

Clearly(?) the documents remove the need for MASC for IPv6. Is that all?
Will uni-based have any effect on MBGP and BGMP?
(I can't find an BGMP draft to even have a peek.)

These questions might seem naïve to you, but I suspect there are implementors 
and operators that might have the same questions.

   Erik

---

From: "Brian Haberman" <[email-masked]>
Date: Wed, 19 Sep 2001 08:04:35 -0400

Erik,

> (I can't find an BGMP draft to even have a peek.)

The text in the draft will be changed to point out how uni-based mcast
removes the need for inter-domain mcast allocation protocols.  From my
point of view, I don't see them really affecting MBGP or BGMP.  From
some discussions I have had with Dave, uni-based mcast MAY help make
BGMP simpler...

> and operators that might have the same questions.

No argument there.  I am trying to find some time this week to make
some updates to these docs so that we can keep them moving.

Brian