Subject: (ngtrans) draft-ietf-ngtrans-6to4-04: multicast and PIM/link-local

From: [email-masked]
Date: Sun, 12 Mar 2000 18:57:58 +0900

6to4 draft (draft-ietf-ngtrans-6to4-04) suggests use of PIM over 6to4
	pseudo link (or cloud).  Could someone clarify how can we really use
	PIM over 6to4 cloud?  PIM uses link-local multicast (ff02::{d,e})
	to detect adjacent PIM router.  It is not possible for 6to4 cloud.

	Section 3.1 talks about link-local address, however, I cannot think
	of possible real use of link-local address over 6to4 cloud.  In what
	situation do we use them?

	BTW, 6to4 04 draft clarifies some of multicast forwarding details.
	Thank you very much for clarification.

itojun

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From: Brian E Carpenter <[email-masked]>
Date: Mon, 13 Mar 2000 10:50:47 -0600

Hi,

>         to detect adjacent PIM router.  It is not possible for 6to4 cloud.

Well, the 6to4 authors are not experts on PIM-SM. We need someone who is
an expert on PIM-SM to help us. How do PIM-SM routers detect each other
over unicast links? Why is it any different over 6to4 virtual unicast links?

>         situation do we use them?

When a 6to4 router talks to another 6to4 router there is a virtual link between
them (it really is a tunnel, but disguised). So it needs a link-local
address for completeness. We need to define it even if we *never* use it,
to respect the IPv6 addressing model.

>         Thank you very much for clarification.

Thanks

  Brian

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From: [email-masked]
Date: Wed, 15 Mar 2000 02:19:23 +0900

>over unicast links? Why is it any different over 6to4 virtual unicast links?

	from what I see from RFC2362 3.1.1, it is not covered in the document.
	(I'm no way expert in PIM)

>to respect the IPv6 addressing model.

	Suppose A and B are 6to4 router.  When A originates packet to B, 
	A needs to avoid using its link-local as source, since B can never
	reply to it.  Do the source address selection rules cover this enough?
	I think it becomes much easier to handle, and safer if we don't
	assign it.

itojun