Re: [netmod] WG Last Call: draft-ietf-netmod-revised-datastores-04 updates

[t.petch]

- Original Message -
From: "Martin Bjorklund" 
Sent: Monday, September 18, 2017 8:58 AM


> "t.petch"  wrote:
> > - Original Message -
> > From: "Martin Bjorklund" 
> > Sent: Sunday, September 17, 2017 2:41 PM
> >
> > > Andy Bierman  wrote:
> > > > On Sat, Sep 16, 2017 at 12:24 AM, Juergen Schoenwaelder <
> > > > j.schoenwael...@jacobs-university.de> wrote:
> > > >
> > > > > On Fri, Sep 15, 2017 at 02:07:58PM -0700, Andy Bierman wrote:
> > > > > > Hi,
> > > > > >
> > > > > > I strongly agree with Tom that the current draft is an
update to
> > RFC
> > > > > 7950.
> > > > > > I also strongly disagree with the decision to omit RFC 2119
in a
> > > > > standards
> > > > > > track document. IMO RFC 2119 terms need to be used in
normative
> > text,
> > > > > > especially when dealing with XPath and YANG compiler
behavior.
> > > > > >
> > > > >
> > > > > RFC 8174:
> > > > >
> > > > >o  These words can be used as defined here, but using them
is
> > not
> > > > >   required.  Specifically, normative text does not require
the
> > use
> > > > >   of these key words.  They are used for clarity and
> > consistency
> > > > >   when that is what's wanted, but a lot of normative text
does
> > not
> > > > >   use them and is still normative.
> > > > >
> > > > >
> > > > So what?
> > > > Existing YANG specifications use RFC 2119 terms.
> > > > This draft uses those terms, just with lower-case.
> > >
> > > Actually, section 5.1 XPath Context in the revised datastore draft
> > > uses the same language as section 6.4.1 XPath Context in RFC 7950.
In
> > > fact, the text in the draft is copied (and adjusted) from RFC
7950.
> >
> > Martin
> >
> > 'Adjusted' might be seen as a weasel word:-)
> >
> >If the XPath expression is defined in a substatement to a
> >   "notification" statement, the accessible tree is the
notification
> >   instance, all state data in the server, and the running
> >   configuration datastore.
> >
> > becomes
> >
> > If the XPath expression is defined in a substatement to a
> >   "notification" statement, the accessible tree is the
notification
> >   instance and all operational state in the server.
> >
> > Goodbye  (well, running configuration in RFC7950).  Is it a
> > material difference? - it will take me a while to work that one out.
>
> The difference is that the xpath expressions no longer sees unused
> configuration in running.  But if the config is used, it exists in
>  under the same path as before, and it is available.
>
> > I focussed on the XPath rules because they seemed the clearest case,
but
> > updating the definitions, and saying this section will replace the
> > definitions in [RFC6241] and [RFC7950] when these documents are
revised
> > seems  well, like an Erratum held for Update i.e. another
Updates.
>
> Are you saying that this is an argument for having "Updates: 7950"?

Yes

Tom Petch

>
> /martin

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Re: [netmod] WG Last Call: draft-ietf-netmod-revised-datastores-04 updates

[Martin Bjorklund]

"t.petch"  wrote:
> - Original Message -
> From: "Martin Bjorklund" 
> Sent: Sunday, September 17, 2017 2:41 PM
> 
> > Andy Bierman  wrote:
> > > On Sat, Sep 16, 2017 at 12:24 AM, Juergen Schoenwaelder <
> > > j.schoenwael...@jacobs-university.de> wrote:
> > >
> > > > On Fri, Sep 15, 2017 at 02:07:58PM -0700, Andy Bierman wrote:
> > > > > Hi,
> > > > >
> > > > > I strongly agree with Tom that the current draft is an update to
> RFC
> > > > 7950.
> > > > > I also strongly disagree with the decision to omit RFC 2119 in a
> > > > standards
> > > > > track document. IMO RFC 2119 terms need to be used in normative
> text,
> > > > > especially when dealing with XPath and YANG compiler behavior.
> > > > >
> > > >
> > > > RFC 8174:
> > > >
> > > >o  These words can be used as defined here, but using them is
> not
> > > >   required.  Specifically, normative text does not require the
> use
> > > >   of these key words.  They are used for clarity and
> consistency
> > > >   when that is what's wanted, but a lot of normative text does
> not
> > > >   use them and is still normative.
> > > >
> > > >
> > > So what?
> > > Existing YANG specifications use RFC 2119 terms.
> > > This draft uses those terms, just with lower-case.
> >
> > Actually, section 5.1 XPath Context in the revised datastore draft
> > uses the same language as section 6.4.1 XPath Context in RFC 7950.  In
> > fact, the text in the draft is copied (and adjusted) from RFC 7950.
> 
> Martin
> 
> 'Adjusted' might be seen as a weasel word:-)
> 
>If the XPath expression is defined in a substatement to a
>   "notification" statement, the accessible tree is the notification
>   instance, all state data in the server, and the running
>   configuration datastore.
> 
> becomes
> 
> If the XPath expression is defined in a substatement to a
>   "notification" statement, the accessible tree is the notification
>   instance and all operational state in the server.
> 
> Goodbye  (well, running configuration in RFC7950).  Is it a
> material difference? - it will take me a while to work that one out.

The difference is that the xpath expressions no longer sees unused
configuration in running.  But if the config is used, it exists in
 under the same path as before, and it is available.

> I focussed on the XPath rules because they seemed the clearest case, but
> updating the definitions, and saying this section will replace the
> definitions in [RFC6241] and [RFC7950] when these documents are revised
> seems  well, like an Erratum held for Update i.e. another Updates.

Are you saying that this is an argument for having "Updates: 7950"?


/martin

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Re: [netmod] WG Last Call: draft-ietf-netmod-revised-datastores-04 updates

[t.petch]

- Original Message -
From: "Martin Bjorklund" 
Sent: Sunday, September 17, 2017 2:41 PM

> Andy Bierman  wrote:
> > On Sat, Sep 16, 2017 at 12:24 AM, Juergen Schoenwaelder <
> > j.schoenwael...@jacobs-university.de> wrote:
> >
> > > On Fri, Sep 15, 2017 at 02:07:58PM -0700, Andy Bierman wrote:
> > > > Hi,
> > > >
> > > > I strongly agree with Tom that the current draft is an update to
RFC
> > > 7950.
> > > > I also strongly disagree with the decision to omit RFC 2119 in a
> > > standards
> > > > track document. IMO RFC 2119 terms need to be used in normative
text,
> > > > especially when dealing with XPath and YANG compiler behavior.
> > > >
> > >
> > > RFC 8174:
> > >
> > >o  These words can be used as defined here, but using them is
not
> > >   required.  Specifically, normative text does not require the
use
> > >   of these key words.  They are used for clarity and
consistency
> > >   when that is what's wanted, but a lot of normative text does
not
> > >   use them and is still normative.
> > >
> > >
> > So what?
> > Existing YANG specifications use RFC 2119 terms.
> > This draft uses those terms, just with lower-case.
>
> Actually, section 5.1 XPath Context in the revised datastore draft
> uses the same language as section 6.4.1 XPath Context in RFC 7950.  In
> fact, the text in the draft is copied (and adjusted) from RFC 7950.

Martin

'Adjusted' might be seen as a weasel word:-)

   If the XPath expression is defined in a substatement to a
  "notification" statement, the accessible tree is the notification
  instance, all state data in the server, and the running
  configuration datastore.

becomes

If the XPath expression is defined in a substatement to a
  "notification" statement, the accessible tree is the notification
  instance and all operational state in the server.

Goodbye  (well, running configuration in RFC7950).  Is it a
material difference? - it will take me a while to work that one out.

I focussed on the XPath rules because they seemed the clearest case, but
updating the definitions, and saying this section will replace the
definitions in [RFC6241] and [RFC7950] when these documents are revised
seems  well, like an Erratum held for Update i.e. another Updates.

Tom Petch


> /martin

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Re: [netmod] WG Last Call: draft-ietf-netmod-revised-datastores-04 updates

[Andy Bierman]

On Sat, Sep 16, 2017 at 3:14 AM, Juergen Schoenwaelder <
j.schoenwael...@jacobs-university.de> wrote:

> On Sat, Sep 16, 2017 at 02:56:45AM -0700, Andy Bierman wrote:
>
> > Either way, the new YANG rules seem half-baked and not ready
> > for standardization.
>
> OK. Then please tell us where you see problems. The usage of must vs
> MUST does not seem to be the issue.
>
>

sec 4.4:

Validation is performed on the contents of .


Does this mean validation is not done on ?
The draft does not say.  If so, then this seems to break all
existing clients that validate . Standard operations
such as  or  with :writable-running capability work
this way.

What happens if a client does validation on ? It now can fail even
though RFC 7950, sec. 8.1 says:

   *The running configuration datastore MUST always be valid.*

The motivation is clear in the RD draft, sec 4.3:

   The running configuration datastore () holds the complete
   current configuration on the device.  It may include inactive
   configuration or template-mechanism-oriented configuration that
   require further expansion.


This forces a client to accept unspecified proprietary inactive
configuration and proprietary templates
that apparently are not subject to YANG validation.

   Currently there are no standard mechanisms defined that affect
so that it would have different contents than ,
   but this architecture allows for such mechanisms to be defined.


This is a significant change in the NETCONF/RESTCONF standards which is
completely unrelated to operational state. The client MUST understand
unspecified
proprietary differences between  and .  The client
can now
assume that  is always valid, but this draft breaks that.

IMO, only the  datastore work is standards-ready.


Andy



/js
>
> --
> Juergen Schoenwaelder   Jacobs University Bremen gGmbH
> Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany
> Fax:   +49 421 200 3103 
>
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Re: [netmod] WG Last Call: draft-ietf-netmod-revised-datastores-04 updates

[Juergen Schoenwaelder]

On Sat, Sep 16, 2017 at 02:56:45AM -0700, Andy Bierman wrote:

> Either way, the new YANG rules seem half-baked and not ready
> for standardization.

OK. Then please tell us where you see problems. The usage of must vs
MUST does not seem to be the issue.

/js

-- 
Juergen Schoenwaelder   Jacobs University Bremen gGmbH
Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany
Fax:   +49 421 200 3103 

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Re: [netmod] WG Last Call: draft-ietf-netmod-revised-datastores-04 updates

[Andy Bierman]

On Sat, Sep 16, 2017 at 12:24 AM, Juergen Schoenwaelder <
j.schoenwael...@jacobs-university.de> wrote:

> On Fri, Sep 15, 2017 at 02:07:58PM -0700, Andy Bierman wrote:
> > Hi,
> >
> > I strongly agree with Tom that the current draft is an update to RFC
> 7950.
> > I also strongly disagree with the decision to omit RFC 2119 in a
> standards
> > track document. IMO RFC 2119 terms need to be used in normative text,
> > especially when dealing with XPath and YANG compiler behavior.
> >
>
> RFC 8174:
>
>o  These words can be used as defined here, but using them is not
>   required.  Specifically, normative text does not require the use
>   of these key words.  They are used for clarity and consistency
>   when that is what's wanted, but a lot of normative text does not
>   use them and is still normative.
>
>
So what?
Existing YANG specifications use RFC 2119 terms.
This draft uses those terms, just with lower-case.
Either way, the new YANG rules seem half-baked and not ready
for standardization.



> /js
>
>
Andy


> --
> Juergen Schoenwaelder   Jacobs University Bremen gGmbH
> Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany
> Fax:   +49 421 200 3103 
>
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Re: [netmod] WG Last Call: draft-ietf-netmod-revised-datastores-04 updates

[Juergen Schoenwaelder]

On Fri, Sep 15, 2017 at 02:07:58PM -0700, Andy Bierman wrote:
> Hi,
> 
> I strongly agree with Tom that the current draft is an update to RFC 7950.
> I also strongly disagree with the decision to omit RFC 2119 in a standards
> track document. IMO RFC 2119 terms need to be used in normative text,
> especially when dealing with XPath and YANG compiler behavior.
>

RFC 8174:

   o  These words can be used as defined here, but using them is not
  required.  Specifically, normative text does not require the use
  of these key words.  They are used for clarity and consistency
  when that is what's wanted, but a lot of normative text does not
  use them and is still normative.

/js

-- 
Juergen Schoenwaelder   Jacobs University Bremen gGmbH
Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany
Fax:   +49 421 200 3103 

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Re: [netmod] WG Last Call: draft-ietf-netmod-revised-datastores-04 updates

[Andy Bierman]

Hi,

I strongly agree with Tom that the current draft is an update to RFC 7950.
I also strongly disagree with the decision to omit RFC 2119 in a standards
track document. IMO RFC 2119 terms need to be used in normative text,
especially when dealing with XPath and YANG compiler behavior.


Andy


On Fri, Sep 15, 2017 at 5:34 AM, Juergen Schoenwaelder <
j.schoenwael...@jacobs-university.de> wrote:

> On Fri, Sep 15, 2017 at 12:19:42PM +0100, t.petch wrote:
> > This I-D updates RFC7950, since it changes the XPath context that YANG
> > uses, yet there is no mention of 'Updates'
>
> I think the editors of the document reached the conclusion that the
> xpath context rules stated in section 5.1. are the only meaningful
> interpretation which is consistent with what RFC 7950 says.
>
> The question is whether the text 'changes' the xpath context, or
> 'refines' the xpath context, or 'clarifies' the xpath context.  On a
> synchronous system (where intended config and applied config never
> differ), there is no change at all.
>
> That said, I have no strong opinion about the question whether section
> 5.1 requires an 'Updates: RFC 7950' or not. I do not think section 5.1
> is relevant for a system that uses RFC 7950 without implementing NMDA
> and hence the value of having a forward pointer from RFC 7950 to NMDA
> is likely not critical to have.
>
> /js
>
> --
> Juergen Schoenwaelder   Jacobs University Bremen gGmbH
> Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany
> Fax:   +49 421 200 3103 
>
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Re: [netmod] WG Last Call: draft-ietf-netmod-revised-datastores-04 updates

[Juergen Schoenwaelder]

On Fri, Sep 15, 2017 at 12:19:42PM +0100, t.petch wrote:
> This I-D updates RFC7950, since it changes the XPath context that YANG
> uses, yet there is no mention of 'Updates'

I think the editors of the document reached the conclusion that the
xpath context rules stated in section 5.1. are the only meaningful
interpretation which is consistent with what RFC 7950 says.

The question is whether the text 'changes' the xpath context, or
'refines' the xpath context, or 'clarifies' the xpath context.  On a
synchronous system (where intended config and applied config never
differ), there is no change at all.

That said, I have no strong opinion about the question whether section
5.1 requires an 'Updates: RFC 7950' or not. I do not think section 5.1
is relevant for a system that uses RFC 7950 without implementing NMDA
and hence the value of having a forward pointer from RFC 7950 to NMDA
is likely not critical to have.

/js

-- 
Juergen Schoenwaelder   Jacobs University Bremen gGmbH
Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany
Fax:   +49 421 200 3103 

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Re: [netmod] WG Last Call: draft-ietf-netmod-revised-datastores-04 updates

[t.petch]

This I-D updates RFC7950, since it changes the XPath context that YANG
uses, yet there is no mention of 'Updates'

Well, a purist will say that people can create and use  models using
RFC7950 with no need to have any understanding of this I-D so
technically no 'Updates' is needed.

But a practical engineer will say that the expectation is that many, if
not most, future models will rely on this I-D and its updates to RFC7950
so to say that you do not need to know about it is just misleading.

I am in the latter camp.

I thought of alternatives.  It is true that new models will have a
Normative Reference to this I-D but I suspect that that will not be
enough to alert users.

RFC6087bis could mention it but that is aimed at producers rather than
consumers who are the ones affected.

So. pragmatically, I think that this I-D needs an 'Updates'.

Tom Petch

- Original Message -
From: "Lou Berger" 
To: "netmod WG" 
Cc: ;

Sent: Friday, September 01, 2017 10:02 PM
Subject: [netmod] WG Last Call: draft-ietf-netmod-revised-datastores-04


> All,
>
> This starts a two week working group last call on
> draft-ietf-netmod-revised-datastores-04.
>
> The working group last call ends on September 17.
> Please send your comments to the netmod mailing list.
>
> Positive comments, e.g., "I've reviewed this document and
> believe it is ready for publication", are welcome!
> This is useful and important, even from authors.
>
> Thank you,
> Netmod Chairs
>
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