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Re: new internet draft - LDAP Extensions Style Guide

At 05:43 PM 8/15/2000 +0100, David Chadwick wrote: 
I agree with Kurt that controls are there to modify individual
operations and therefore putting them on the Bind is a nonsense.

I would not say that it is "a nonsense". As it stands now, the Bind Operation does have an affect on every succeeding operation. For example, the identity and the authentication mechanism in the Bind will result in different privileges and levels of access to the directory information. It seems natural to me to include at the time of the bind a list of Controls that the client is willing to accept from the server. The alternatives are I see it are:

- don't ever let the client tell the server
- include a list of acceptable controls with each operation request, assuming that the server is really stupid, and
can't remember the list from one operation to the next.
- define a new extended operation that allows the client to submit a list of acceptable controls

I seem to remember in one of the draft versions of RFC 2251 that there was a way to set client options/defaults. I'd thought that it was in the Bind someplace, but was later dropped. Maybe one of the Marks (Smith or Wahl) can remember better (not that history matters that much). This gives a way of allowing for controls which are not specifically solicited to be returned by the server, without the client having to specifically request them.

Perhaps it doesn't matter too much (as you say below), if each control definition includes the list of valid other controls that may be returned in the response, and unsolicited, unsupported controls are always ignored by the client. Hopefully, the interaction amongst controls will not become too complex in the future.

The client may perform some operations and not want the controls
to take effect (e.g. duplicate entries) even though it supports them.

Thus a server should not send controls to the client if the client has
not used them first on the operation. It follows from this that each
operation request control needs to clearly specify which response
controls may be applied by the server, but I guess we are already
doing this in our extensions, although sometimes it might be implicit.
This will need to be checked as the IDs move to proposed standard.

David

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David Chadwick
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