Subject: MLDv2 and RFC2461bis

From: Elwyn Davies <[email-masked]>
Date: Mon, 11 Jul 2005 16:54:31 +0100

Late breaking thought...

Paragraph 2 of Section 7.2.1 of draft-ietf-ipv6-2461bis-03.txt says that 
joining and leaving the solicited-node multicast group SHOULD be done 
using MLD (and the reference is to RFC2710 i.e., MLDv1).  We now have 
MLDv2.. RFC3810.. Should something be said about this?

If I understand the compatibility section RFC3810 correctly, if hosts 
continue to generate MLDv1 Listener Reports the routers will be forced 
to operate in MLDv1 compatibility mode for the solicited-node multicast 
addresses, perpetuating this mode for ever.  Is this desirable?  
Presumably this can only be handled by providing a configuration flag 
which would tell an interface to send MLDv2 Listener Reports instead of 
MLDv1 ones.

Regards,
Elwyn Davies

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From: Brian Haberman <[email-masked]>
Date: Mon, 11 Jul 2005 17:44:20 -0400

On Jul 11, 2005, at 11:54, Elwyn Davies wrote:

> Late breaking thought...
>
> Paragraph 2 of Section 7.2.1 of draft-ietf-ipv6-2461bis-03.txt says 
> that joining and leaving the solicited-node multicast group SHOULD be 
> done using MLD (and the reference is to RFC2710 i.e., MLDv1).  We now 
> have MLDv2.. RFC3810.. Should something be said about this?

Since the MLD reference is Informative, it could be augmented to mention
both 2710 and 3810.

> to operate in MLDv1 compatibility mode for the solicited-node 
> multicast addresses, perpetuating this mode for ever.  Is this 
> desirable?  Presumably this can only be handled by providing a 
> configuration flag which would tell an interface to send MLDv2 
> Listener Reports instead of MLDv1 ones.
>

The main, current benefit of MLDv2 is to support source-specific 
multicast
(SSM).  However, the NDP use of multicast is non-SSM (ASM or any-source
multicast) and does not need MLDv2 capability in order to function 
correctly.

I would support adding an additional reference to 3810 in order to 
encourage
implementors to move up in capability.

Regards,
Brian

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From: Stig Venaas <[email-masked]>
Date: Mon, 11 Jul 2005 23:53:28 +0200

On Mon, Jul 11, 2005 at 05:44:20PM -0400, Brian Haberman wrote:
[...]
> multicast) and does not need MLDv2 capability in order to function 

Yes, so not important, but...

> implementors to move up in capability.

I also think we should encourage this. Might then be able to get rid of
MLDv1 and simplify things later on (well, might take a very long time).

Stig

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From: Elwyn Davies <[email-masked]>
Date: Mon, 11 Jul 2005 23:06:02 +0100

My understanding that as well as a reference to MLDv2 we would need to 
mention that if any of the routers are 'legacy' that support only MLDv1, 
then any MLDv2 routers would have to have their configuration flags set 
to make them operate in MLDv1 compatibility mode.  Hosts on the other 
hand willl behave correctly whether they are MLDv2 or only MLDv1 capable.

Regards,
Elwyn

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From: Brian Haberman <[email-masked]>
Date: Mon, 11 Jul 2005 18:16:03 -0400

On Jul 11, 2005, at 18:06, Elwyn Davies wrote:

> mention that if any of the routers are 'legacy' that support only 
> MLDv1, then any MLDv2 routers would have to have their configuration 
> flags set to make them operate in MLDv1 compatibility mode.  Hosts on 
> the other hand willl behave correctly whether they are MLDv2 or only 
> MLDv1 capable.

I don't think we want to add MLD configuration guidance in 2461bis.  If 
someone is
running a mix of MLDv1 and MLDv2 routers, they need to be aware of the 
operational
guidance provided in RFC 3810.

Brian

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From: Stig Venaas <[email-masked]>
Date: Tue, 12 Jul 2005 00:23:21 +0200

> guidance provided in RFC 3810.

Also, the issue with MLDv1 and MLDv2 routers on the same link is totally
independent of this. Whenever you mix such routers on a link you need to
do this and it is not for specific groups either. So routers would have
to be configured the same independent of what 2461bis says.

Stig