[openib-general] [RFC] ib_mad

[Hal Rosenstock]

On Thu, 2004-09-16 at 20:51, Roland Dreier wrote:
> By the way, I'm not sure I totally understand the IB spec on pluggable
> ports.  Is the idea that the number of ports can change or just that
> the GUID of a port might change?

The short answer is that both can change. 

While the IB spec indicates GUIDs (there are 3 levels of management
GUIDs: system image, node, and port) are manufacturer assigned, it is up
to the manufacturer as to how they are assigned. Clearly, system image
GUIDs can change as there is an optional trap for this. I am not sure
there is an explicit requirement to keep node and port GUIDs the same.
However, changing them has an effect on IB management (e.g. SM) and
should not be taken lightly.

For any hot swappable "component", there needs to be some persistent
uniquifier to identify it's "physical"ness. In ethernet that is the MAC
address. In IB, it is likely a GUID. That would be the ModuleGUID (in
vol 2). ChassisGUID would be the chassis into which the module is
plugged. If the IB device (xCA, switch) are permanently affixed to a
chassis (there are compliances for this), the Chassis and ModuleGUIDs
can be the same. These are contained in ChassisInfo and ModuleInfo
attributes obtainable by the BM. Based on the (IB) module and chassis
type, one or both of these are required. (I'm much less "fluent" here). 

Does that make sense ? Or is it more confusing ? Does that answer your
question ?

-- Hal