Subject: mboned: draft-ietf-mboned-ipv6-multicast-issues-02.txt

From: "Molina, Angel (Angel)" <[email-masked]>
Date: Thu, 13 Oct 2005 07:38:20 +0200

mboned experts,

while reading draft-ietf-mboned-ipv6-multicast-issues-02.txt I came across the passage quoted below (section "4.2  Neighbor Discovery Using Multicast"). It's quite likely I'm missing something trivial, but I'm having trouble figuring out how the problem hinted at in the passage can come about. 

- Why would such an IGMP-snooping switch fail to forward IPv6 frames? 

Any hint would be much appreciated. A reference to some document or earlier post describing this problem would also do it, of course.

Thanks in advance and regards,
Angel Molina

--- begin quote ---
"In some Ethernet switches, IPv6 frames are likewise not forwarded.
   The problem has likely been with building multicast forwarding state
   based on Layer 3 information (which the vendor does support with
   IPv6); state using Layer 2 information would work just fine
   [I-D.ietf-magma-snoop].  Therefore the snooping swich developers
   should be aware of the tradeoff of using Layer 2 vs Layer 3
   information on multicast data forwarding, especially if IPv6 snooping
   is not supported."
--- end quote ---

-----------------------------------------
Angel Molina
Lucent Technologies
Systems Engineering, Network Solutions Group
Shanghai, PRC

Voice:  +86 21 5450 4555 Ext. 5530
E-Mail: [email-masked]

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---

From: Pekka Savola <[email-masked]>
Date: Thu, 13 Oct 2005 09:14:56 +0300 (EEST)

Hi,

On Thu, 13 Oct 2005, Molina, Angel (Angel) wrote:
> while reading draft-ietf-mboned-ipv6-multicast-issues-02.txt I came 
> across the passage quoted below (section "4.2 Neighbor Discovery 
> Using Multicast"). It's quite likely I'm missing something trivial, 
> but I'm having trouble figuring out how the problem hinted at in the 
> passage can come about.
>

If the snooping switch were to do IP-based snooping, just by looking 
at the IGMP reports, and discarding other multicast (including v6 
multicast), obviously there would be a problem, right?

Also obviously, if the switch were to do look for IGMP reports, 
discarding other *IPv4* multicast, but flooding v6 multicast on all 
ports, v6 multicast would work (though v4 multicast might be hampered 
if IGMPv3 would not be supported).

Does this clarify the (potential) problem?

NB: the document has been discontinued, and should be reworked into 
something a bit different.  I haven't wanted to do that as folks don't 
seem too interested in doing the work.  Anyone can feel free to pick 
up the ball.

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