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

From: "jspark" <[email-masked]>
Date: Fri, 24 Oct 2003 19:55:52 +0900

-----Original Message-----
From: jspark [mailto:[email-masked]] 
Sent: Friday, October 24, 2003 7:51 PM
To: 'Pekka Savola'
Cc: [email-masked]'; [email-masked]'

Hi Pekka. 

On Fri, 24 Oct 2003, Pekka Savola wrote:
> First, there is typically just one link-local address.  
> Either it uses EUI-64 based IID or not.  

Right.

So many types of addresses exist
such as stateless, stateful, manually etc.

> If it doesn't, you can't generate addresses like this.

In our spec,
we mentioned that EUI-64 IID based LL address is only used.

But, I think that stateful or manually configured addresses are also useful
because these kinds of addresses are supported by DAD. 

> Second, the EUI-64 does not guarantee the uniqueness of the method.  
> Otherwise we would not be needing DAD with addresses that are 
> generated with EUI-64.

Right.

The EUI-64 itself is not unique.
So, DAD procedure is needed for link-local address.
And also stateful or manually configured addresses are used after DAD
processing.

> 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.

Jungsoo.

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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

---

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

> our method supposes that LL unicast address should be verified by DAD

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