[openib-general] IPv6 and IPoIB scalability issue

[Hal Rosenstock]

On Fri, 2006-12-01 at 17:26, Roland Dreier wrote:
>  > Option 1 sounds difficult to me. It would be hard to have interop
>  > between nodes using this optimization and nodes that don't..
> 
> Yes, that is a major problem.
> 
> One intermediate thing we could do is to have nodes join their own
> solicited-node group as a full member, but have other nodes send ND
> messages to the all-nodes group.  Then the SM would only have O(N)
> MCG memberships to maintain.  But it still requires the SM to be smart
> about mapping multiple MCGs to a single MLID.
> 
> And even if that works, I'm not sure it's compliant with all the
> relevant RFCs, and it might break in some strange situations...
> 
> (To be honest though, I think that the SM for a subnet with N nodes
> should really be beefy enough to handle N^2 multicast memberships.
> Even 10K nodes leads to only 100M group memberships, which shouldn't
> be _that_ expensive with the right data structures)

The data structures are one concern. The others would be routing N large
(multicast) trees and also the SA transaction rate this causes (similar
to the large path record request case).

-- Hal

>  - R.