[ofa-general] Re: [RFC] OpenSM and IPv6 Scalability Proposal

[Jason Gunthorpe]

On Sat, May 09, 2009 at 01:32:06PM +0300, Eli Dorfman wrote:
> On Fri, May 8, 2009 at 4:57 PM, Hal Rosenstock <hal.rosenstock at gmail.com> wrote:
> > On Wed, May 6, 2009 at 6:24 AM, Slava Strebkov <slavas at voltaire.com> wrote:
> >>
> >> In addition to the original proposal we suggest allocating special MLID
> >> for the following MGIDs:
> >> ??1. FF12401bxxxx000000000000FFFFFFFF - All Nodes
> >> ??2. FF12401bxxxx00000000000000000001 - All hosts
> >> ??3. FF12401bffff0000000000000000004d ??- all Gateways
> >> ??4. FF12401bxxxx00000000000000000002 - all routers
> >> ??5. FF12601bABCD000000000001ffxxxxxx - IPv6 SNM
> >
> > It turns out that collapsing multicast groups across PKeys on a single
> > MLID may not be such a good idea unless partition enforcement
> > enforcement by switches is disabled. There should be different modes
> > of collapsing based on this based on whether this is enabled or not.
> 
> The idea is to allocate a different MLID per each of the above special MGIDs.

In practice I think you'd be better to combine the All Nodes, All
hosts, All Gatesways, All Routers and IPv4 broadcast group onto a
single MLID and then distribute the SNM groups over some number of
additional MLIDs in an intelligent manner. The specialty groups are
not really used very much, while the purpose of the SNM group is for
ND scalability.

If your network is large enough to care about this then it is probably
also large enough to benefit from multiple SNM groups..

Otherwise, you may as well lump them all together into the broadcast
MLID.

Jason