Subject: RE: Proposed dynamic partitioning architecture

From: "Anderson, Todd A" <[email-masked]>
Date: Tue, 9 Jan 2001 17:11:24 -0800

> on the one hand, if i understand the concept of
> "dynamic partitioning" correctly, the spm is always a
> higher authority than any controller. on the other, a
> partition is subservient to its controller and has no
> business withdrawing resources in use. so it seems to
> me that a switch should refuse such a conflicting
> request from an spm on the grounds that the spm must
> resolve the conflict with the respective controller
> before withdrawing the switch resources. the means of
> such resolution being outside of gsmp.

IMHO, the switch should not withdraw resources that are in use.
Convincing the controller to give up those resources so that
they can be repartitioned is outside the scope of GSMP and
the partitioning data model.

> however, in this proposal there is a burden on the
> switch since it is required to be able to detect the
> conflict: a thoroughly non-trivial task. this is bad
> because it's an expensive error check for a condition
> that should never happen.

Could you give an example of where this check is non-trivial?
Most of the cases seem to be one of table space.  In order
to enforce the original partitioning, the switch must be aware
of which partition owns each table entry (or at least how many
entries in the table a partition owns).  In either case, I can
tell whether a repartitioning would exceed an allocated number
of table entries.  Am I missing something here?  Is there
something harder than table space that we are dealing with?

> what are the alternatives? if the spm really is
> superior to all controllers and we assume its sanity
> (as we always do with controllers in the gsmp model)
> then we could suppose that the spm has good reason to
> take the action of removing resources in use by a
> controller, e.g. the controller is not co-operating
> for whatever reason. so the switch removes the
> impacted connection state and repartitions.

Let's say I decrease the number of labels I can allocate
on a port.  The new number of labels assigned to that
port is below the number of current labels in use.  Which
connections do I disconnect?  I can't think of a good way
to make that decision.  Also, I don't think I'd characterize
the spm as superior to all controllers.  The two controllers
have different functionality.  I think the solution to a
misbehaving controller is replacing/reconfiguring it rather
than choking it by decreasing the resources it has to work
with.

> coming back to the first model: if an spm is unable
> to cajole a controller into releasing switch resources,
> what is it do? this question is not really a gsmp
> question, although the answer may have impact on gsmp,
> but it highlights how we need more discussion on the
> architectural requirements of "dynamic partitioning."

There may be only an indirect connection between the SPM
and the GSMP controller.  At first, they may be intermediated 
by a pair of administrators.  One calls the other and requests
a partition and then later decides they have overallocated and
calls to reduce the resources.  The SPM administrator instructs
the SPM to reduce the resources devoted to the partition and
the switch informs the SPM that this is impossible because the
resources are currently in use.  The SPM administrator contacts
the GSMP admin who now has to force GSMP to release switch
resources.  How does he do this?  If he has a way to break the
connections to free resources they may be used again before
the SPM can reattempt the repartition.  It appears the GSMP
admin needs a way to tell the GSMP controller not to use all
of the resources reported by the switch.  Thus, it appears
this affects the implementation of the controller but I haven't
found any changes need to GSMP although they could be lurking.

> > The only change that this architecture forces upon GSMP is that the
> > switch needs to be able to inform the controller of a change in
> > resources.  Are there any suggestions as to how to do this?
> i'd prefer an explicit notification.

As do I.

---

From: "Avri Doria" <[email-masked]>
Date: Sat, 27 Jan 2001 11:43:22 +0100

> the partitioning data model.

On the other hand if the partitioning authority had the means
of notifying the controller that a partition was frozen in anticipation
of reassignment of resources (the notion of no more adds), that 
controller could begin to release resources.  You are right that this
does not constitute 'convincing' the controller.  Rather it is a
notification that could kick off some previously installed (by a
separate policy/management means ) behavior.

> > that should never happen.

Doesn't the switch have to know if some entity other then
the controller set changes its resource set?
 
> connections do I disconnect?  

I don't think you should be able to withdraw labels that are in use.
That is, are allocated to active or reserved connections.

> I can't think of a good way
> resources are currently in use.  

Do you mean currently in use, or currently allocated, whether they 
are in use or not?

> The SPM administrator contacts
> the SPM can reattempt the repartition.  

I don't think that GSMP should ever be forced to release connection
state except by a controller.

On the other hand, we have to be aware of is that other entities 
might also have the ability to change the activities of a partition - 
for example a command line interface.  As far as GSMP is concerned, 
this would constitute an event that should cause notification of
the controller(s).
  
> It appears the GSMP

> > i'd prefer an explicit notification.

What exactly do you mean by an explicit notification?
do you mean a 'resources changed' alarm?
or do you mean an explicit list of all changed resource
levels? 

a.
-- 

Avri Doria
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