[ofa-general] opensm: Unsupported attribute = 0xFF02

[Hal Rosenstock]

On Thu, 2007-11-01 at 09:48 -0700, Sean Hefty wrote:
> > As mentioned in the past, client reregistration is a rather large
> > hammer. There have been discussions on utilizing this mechanism in more
> > scenarios (which FWIW is not a good thing IMO). This approach (and it is
> > optional) pushes the burden back on the end nodes rather than the SM.
> > Scalability is certainly an issue with it. It was begrudgingly put into
> > the spec. It was intended only as a stopgap measure.
> > 
> > There was informative text put into the spec alluding to the
> > "appropriate" use of this option:
> > 
> > "A reason for the SM doing this might be that the SM suffered a failure
> > and as a result lost its own records of such subscriptions."
> > This is referring to a single SM (although that is not the recommended
> > deployment topology) crashing and being restarted.
> > 
> > IMO a civil SM would not rely on this mechanism.
> 
> There's still the problem that the ULPs on the end-node do not know when 
> or if the data is lost.

Such data is not supposed to be lost although this is left as an
exercise to the reader. That is all beyond the spec value add currently.

> IMO, making client reregistration mandatory

Couldn't be done due to backwards compatibility guarantee of IBA.
 
> would have been a better solution, allowing ULPs to only re-register on 
> that event.  As it stands now, ULPs automatically reregister on SM LID 
> changes, port events, etc..  In order to avoid ULP re-registration, SM 
> failover has to bring along the LID.

In general, it does. Most SMs do not change LIDs unless they absolutely
have to. Using reregister for this (and some other point cases) would be
fine but not in the general case of failover for all ports.

> An alternate solution could have let an SM learn what it needed from the 
> end nodes through queries...

Currently, SA queries are from the client (end node) to the SA; not the
other way around. The only thing from the SA to the end node are
reports. That could be changed if it really is needed.

-- Hal

> - Sean