Re: [i2rs] Comments on Ephemeral-REQ-07 (local config vs. ephemeral)

Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de> Wed, 20 July 2016 11:19 UTC

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Date: Wed, 20 Jul 2016 13:19:15 +0200
From: Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>
To: Susan Hares <shares@ndzh.com>
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Mail-Followup-To: Susan Hares <shares@ndzh.com>, "'Joel M. Halpern'" <jmh@joelhalpern.com>, 'Joe Clarke' <jclarke@cisco.com>, 'Russ White' <7riw77@gmail.com>, i2rs@ietf.org
References: <fc5d171b-82da-0041-3248-8a01d31e9202@cisco.com> <016201d1e11b$6c0c3140$442493c0$@ndzh.com> <5a2feb3c-9f9b-8d4a-91f2-db337d1ceecf@cisco.com> <009801d1e24d$3b92a340$b2b7e9c0$@gmail.com> <019b01d1e24e$8ea9bc70$abfd3550$@ndzh.com> <99078e75-8c89-ee08-9ea3-a5d2c0840671@cisco.com> <009201d1e25a$35af9b10$a10ed130$@ndzh.com> <c2f0dbb8-c558-b738-6241-40fc1cd61349@cisco.com> <be18c19b-6b54-fa7c-a6a2-a1d3af8c107d@joelhalpern.com> <001a01d1e274$63dbfbe0$2b93f3a0$@ndzh.com>
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Cc: 'Joe Clarke' <jclarke@cisco.com>, "'Joel M. Halpern'" <jmh@joelhalpern.com>, 'Russ White' <7riw77@gmail.com>, i2rs@ietf.org
Subject: Re: [i2rs] Comments on Ephemeral-REQ-07 (local config vs. ephemeral)
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What is the purpose of the word 'individual' in the sentence? Why does
it talk about 'changes'? Isn't it simply the data that takes
precedence? Or is the idea to have this linked to changes of data,
i.e., how a change was carried out?

I actually find the text related to this in RFC 7921 more helpful
since RFC 7921 provides more insight that priority is associated
with an I2RS client. Perhaps Req-07 should just say:

  Req-07: The I2RS protocol MUST support a priority mechanism to
  resolve any possible conflicts with local configuration as described
  in RFC 7921.

This way we avoid having multiple definitions that may interact in
weird ways. (This might also apply to other requirements where perhaps
a simple pointer to RFC 7921 would be easier and safer than attempts
to reformulate things.)

/js

PS: I do not want to further complicate things so please feel free
    to ignore this.

On Wed, Jul 20, 2016 at 06:49:27AM -0400, Susan Hares wrote:
> I'm fine with this revision.  Anyone else wish to change this version? 
> 
> Sue 
> 
> -----Original Message-----
> From: i2rs [mailto:i2rs-bounces@ietf.org] On Behalf Of Joel M. Halpern
> Sent: Wednesday, July 20, 2016 5:25 AM
> To: Joe Clarke; Susan Hares; 'Russ White'; i2rs@ietf.org
> Subject: Re: [i2rs] Comments on Ephemeral-REQ-07 (local config vs.
> ephemeral)
> 
> That wording may well lead readers to think that Ephemeral configuration,
> considered as a whole, has a priority.  Since that is not true, I would like
> to further refine this.  How about:
> 
> Req-07: Local configuration MUST have a priority that is comparable with the
> I2RS Agent priority for making changes.  This priority will determine
> whether local configuration changes or individual ephemeral configuration
> changes take precedence.  The I2RS protocol MUST support his mechanism.
> 
> Yours,
> Joel
> 
> On 7/20/16 4:05 AM, Joe Clarke wrote:
> > On 7/20/16 03:42, Susan Hares wrote:
> >> Joe:
> >> Yes - you are correct.  Can you help me state this requirement -07 
> >> better?
> >
> > What about:
> >
> > Ephemeral-REQ-07: Ephemeral configuration and local configuration MUST 
> > each have a priority.  This priority will determine whether ephemeral 
> > configuration or local configuration take precedence.  The I2RS 
> > protocol MUST support this mechanism.
> >
> > Is this clear and correct enough?
> >
> > Joe
> >
> >>
> >> Sue
> >>
> >> -----Original Message-----
> >> From: Joe Clarke [mailto:jclarke@cisco.com]
> >> Sent: Wednesday, July 20, 2016 3:40 AM
> >> To: Susan Hares; 'Russ White'; i2rs@ietf.org
> >> Subject: Re: [i2rs] Comments on Ephemeral-REQ-07 (local config vs.
> >> ephemeral)
> >>
> >> On 7/20/16 02:18, Susan Hares wrote:
> >>> <WG hat off> <author hat on>
> >>>
> >>> Here's text that might replace it:
> >>>
> >>> Ephemeral-REQ-07: Ephemeral configuration state MUST be able to set 
> >>> a priority on local configuration and ephemeral state.  Based on 
> >>> this priority implementations MUST be able to provide a mechanism to 
> >>> choose which takes precedence. The I2RS Protocol MUST be able to 
> >>> support this
> >> mechanisms.
> >>>
> >>> Any thoughts?
> >>
> >> I'm a bit confused by the first sentence.  I think what you're 
> >> stating is that both ephemeral and local configurations MUST have a
> priority.
> >> This priority will determine whether ephemeral configuration or local 
> >> configuration take precedence.  The I2RS protocol MUST support this 
> >> mechanism.
> >>
> >> Am I correct in my interpretation?
> >>
> >> Joe
> >>
> >>>
> >>> Sue
> >>>
> >>> -----Original Message-----
> >>> From: Russ White [mailto:7riw77@gmail.com]
> >>> Sent: Wednesday, July 20, 2016 2:09 AM
> >>> To: 'Joe Clarke'; 'Susan Hares'; i2rs@ietf.org
> >>> Subject: RE: [i2rs] Comments on Ephemeral-REQ-07 (local config vs.
> >>> ephemeral)
> >>>
> >>>
> >>> (wg chair hat off) --
> >>>
> >>>> I think the idea of extending I2RS priority to local config 
> >>>> operators
> >>> (e.g., CLI)
> >>>> will still work.  Let's take knob 1.  Knob 1 is kind of like the 
> >>>> on/off
> >>> switch.  If I
> >>>> don't want I2RS to have any effect on operational state, I'd have 
> >>>> this
> >>> off.  In
> >>>> the I2RS priority case, by default my local config could will have 
> >>>> the
> >>> highest
> >>>> priority (let's say that's 255 to make it concrete).  In this case 
> >>>> no
> >>> ephemeral
> >>>> config can win.
> >>>
> >>> I wanted to extend Joe's remarks a bit... On reflection, I actually 
> >>> think having priority + "this wins" bits is rather confusing, and 
> >>> opens the door to all sorts of strange behavior. Say I have two 
> >>> items thus --
> >>>
> >>> Local config item -- priority 100
> >>> I2RS config item -- priority 200, don't overwrite bit set
> >>>
> >>> If the higher priority is supposed to win, then which item should 
> >>> the operator find in the resulting running config? Should it be the 
> >>> I2RS version, because the priority is higher, or the local config, 
> >>> because the "don't overwrite" bit is set? There doesn't seem to be 
> >>> any clear way to interpret such a situation.
> >>>
> >>> It's better to have a single "thing" that determines which 
> >>> configuration among many wins, rather than two.
> >>>
> >>> -r
> >>>
> >>>
> >>
> >>
> >
> > _______________________________________________
> > i2rs mailing list
> > i2rs@ietf.org
> > https://www.ietf.org/mailman/listinfo/i2rs
> >
> 
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-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: +49 421 200 3587         Campus Ring 1 | 28759 Bremen | Germany
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