Re: Partially suppported supportedControl/supportedExtension

["Kurt D. Zeilenga" <Kurt@OpenLDAP.org>]

First, let me clarify the particular problem case:
  The client provided an advertised critical control to a
  search operation.  The server responded with
  unavailableCriticalExtension.

I would argue that advertisement implies the server
recognizes and understands the control (that is,
it is 'supported') BUT that the advertisement
doesn't necessarily imply that any particular
operation extended by the control is serviceable.
However, if not serviceable (for whatever reason),
the server should return a service error, such as
unwillingToPerform, not unavailableCriticalExtension.

This problem is likely the result of language in some
control specifications which suggests returning
unavailableCriticalExtension in cases where the
server cannot service the operation as extended
by the controls.  I view these specifications
to be flawed.

Anyways, I think [Protocol, 4.1.12] is fine here.
However, the description of unavailableCriticalExtension
in [Protocol, A.2] needs a bit of work as "unable or
unwilling to perform" implies a service error.
Instead,
   unavailableCriticalExtensions
	Indicates a critical control is unrecognized
	(see Section 4.1.12).