Subject: Re: FW: IPv6 w.g. Last Call on "Link Scoped IPv6 Multicast Addresses"

From: Jerome Durand <[email-masked]>
Date: Fri, 24 Oct 2003 15:04:44 +0200

Hi

I don't get:

   1°) The need for such link-local adresses. Maybe it should be 
described in the document (saying you will not need any allocation 
server or equivalent is not enough I think). What type of applications 
you think will need these link-local adresses?

   2°) Why to use the flag bit P for these adresses. This bit is already 
clearly defined in the RFC 3306. I don't see the interest in having an 
exception for this RFC if scope <= 2. We already have a lot of 
complexity for IPv6 multicast adresses and poor usage. I would prefer we 
have one way to allocate the adresses and that people can implement it 
easily.

Could you please clarify these points ?

Regards

Jerome

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From: Pekka Savola <[email-masked]>
Date: Fri, 24 Oct 2003 16:20:08 +0300 (EEST)

On Fri, 24 Oct 2003, jspark wrote:
> > But it is mandated by the specs.  So
> > these addresses are
> > *not* truly, completely, totally, unique.
> 
> In our spec.
> The uniqueness of LL unicast address is verified by DAD procedure.
> And then, EUI-64 IID (or other) is extracted from LL Unicast address.
> 
> Therefore,
> our method supposes that LL unicast address should be verified by DAD
> procedure.

Yes.  But the DAD procedure confirmed that the link-local address was 
unique (at that point).  That does not guarantee that the _EUI-64_ part of 
it is unique -- the mechanism is not using the whole link-local address 
here!

No amount of DAD with LL unicast addresses is going to change this :-)

This is mostly just a theoretical discussion, but the real point is -- 
there is no need to _specify_, using _standards action_ a deterministic 
mapping for the link-local multicast addresses.  Just invent one and be 
done with it.. :-)

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings