Re: Separation of configuration and control - good or bad?

[Rob Enns <rpe@juniper.net>]

On Fri, May 16, 2003 at 04:34:01PM -0400, Larry Menten wrote:
> 
> Phil Shafer wrote:
> 
> >Larry Menten writes:
> > 
> >>The Enns model is one in which
> >>configuration is expressed as the transformation of a document.  This is 
> >>why
> >>you must lock the document before you operate on it.
> >>   
> >>
> >
> >Regardless of the configuration change you are making, locking the
> >device seems like a requirement. This seems independent of your
> >view of configuration-as-tree .vs. configuration-as-hierarchy
> >.vs. configuration-as-set-of-strings. If you can't lock it,
> >you can't prevent other sources of configuration (applications or
> >users) from turning your change from benign to dangerous.
> > 
> >
> I disagree.  It should be safe to, for example, delete an OSPF interface 
> instance
> without having to lock the config to do so.  

Why is this not safe with xmlconf?

It happens to make sense to be able to lock a configuration, in a world 
with or without xmlconf. But I don't believe the draft requires it.

> The requirement for locking 
> is an
> artifact of the Enns representation and not inherent to the delete 
> operation.
 
Does the SOHO device you're considering permit only one management
session at a time?

> The Enns spec turns a benign change into a dangerous one.  Just my point.

The protocol spec tries to accomodate the known device configuration
models (single cfg store+immediate operations, candidate 
config+commit+rollback, etc) and not inhibit development of new ones. 
But it doesn't change the basic rules of interaction with devices 
offering a given model.

Can you explain why identifying the target of an operation using
a tag hierarchy as in the draft is dangerous and requires locking, 
while using an xpath subset equivalent does not?

thanks,
 Rob


> >Thanks,
> >Phil
> >
> >--
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> > 
> >
> Thanks,
> Larry
> 
> -- 
> Larry Menten               Lucent Technologies/Bell Laboratories
> Phone: 908 582-4467        600 Mountain Avenue, Murray Hill, NJ  07974 USA 
> 
> 
> 
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