Re: [lmap] Feedback on draft-eardley-lmap-terminology

[Juergen Schoenwaelder <[e-mail]>]

On Thu, Jul 25, 2013 at 02:40:28PM +0100, Paul Aitken wrote:
> >A potential
> >problem with this is that there are likely instructions and tests that
> >do impact each other through side effects.
> >
> >    If C1 schedules a test to be started every 5 min past the hour that
> >    requires no cross traffic while C2 schedules a test to measure
> >    video streaming capabilities during the interval 3-7 minutes past
> >    the hour, then C1 will be surprised that the scheduled test never
> >    executes or produces wrong results.
> 
> Forget about multiple controllers: this situation could arise from a
> single controller.
> 
> So a rejection mechanism will surely be necessary regardless of
> whether there are one or multiple controllers:
>     - whether the command protocol is two-way, so the command is
> immediately rejected.
>     - or, the report protocol includes a way of reporting that the
> requested test could not be done.
>     - or both.

[...]

> If an MA may be commanded to perform multiple tests¹ by a single
> controller, then the potential conflicts are the same as multiple
> tests from multiple controllers.
> 
> ¹ This is necessary if we are to build complex tests out of simpler
> test primitives, eg DNS lookup followed by file download.

Yes, but in this case, it is a single active controller making a
mistake and thus this is likely easier to debug and deal with compared
to multiple controllers 'fighting' over the resources of a MA. If we
design for multiple active controllers, we need to build the necessary
coordination primitives right into the MA for version 1.0, something I
would prefer to avoid since I have the feeling that this adds
complexity and will likely delay things.

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: [phone]         Campus Ring 1, 28759 Bremen, Germany
Fax:   [phone]         <http://www.jacobs-university.de/>