[openib-general] IPv6 and IPoIB scalability issue

[Jason Gunthorpe]

On Fri, Dec 01, 2006 at 03:07:23PM -0500, Hal Rosenstock wrote:

> > total of 2000*2005 (4,010,000) multicast member records in SA for fabric
> 
> This is based on the above (which I'm not sure about) and is the worst
> theoretical case, not the practical case.

It isn't in the IB spec, but what would really help here is to be able
to join a multicast prefix (more than 1 group with a single entry).

Todd's option 1 optimization is then easially realized by having all
IPv6 nodes join FF02::1:FF00:0/104 (all 2**24 multicast entries) as
full members. This provides interoperability between with stacks with
this feature and without.

Option 2 works better as well because all the nodes join
FF02::1:FF00:0/104 as a send-only member on startup and then you only
get N*2 multicast records to maintain.

This also would improve the performance of IPv6 ND by not having to
join/leave the SN groups for each ND query.

IBA would have to be changed to support a prefix bits field in the
MCMemberRecord structure though..

Jason