Re: [netmod] AD review of draft-ietf-netmod-nmda-diff-07

Andy Bierman <andy@yumaworks.com> Mon, 15 March 2021 23:07 UTC

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From: Andy Bierman <andy@yumaworks.com>
Date: Mon, 15 Mar 2021 16:07:11 -0700
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To: joel jaeggli <joelja@gmail.com>
Cc: "Rob Wilton (rwilton)" <rwilton@cisco.com>, NetMod WG Chairs <netmod-chairs@ietf.org>, "draft-ietf-netmod-nmda-diff.all@ietf.org" <draft-ietf-netmod-nmda-diff.all@ietf.org>, "netmod@ietf.org" <netmod@ietf.org>
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Subject: Re: [netmod] AD review of draft-ietf-netmod-nmda-diff-07
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On Mon, Mar 15, 2021 at 10:29 AM joel jaeggli <joelja@gmail.com> wrote:

> yeah when there is an update we'll probably drop a  reminder in the list
> along with a link to the diff, but unless it looks major  there's not
> reason to ask for re-approval.
>
>

It is actually a much more minor change than I thought when I first looked
at it.
The new way is better because the origin tracking feature is optional and
the
current draft ignores this YANG feature.



> thanks
> joel
>

Andy


>
> On Mon, Mar 15, 2021 at 10:26 AM Rob Wilton (rwilton) <rwilton@cisco.com>
> wrote:
>
>> Hi Andy,
>>
>>
>>
>> FYI, this issue was discussed in the Netmod session on Friday.
>>
>>
>>
>> My interpretation of the chairs position is (
>> https://www.youtube.com/watch?v=glLcpQ9kpv0, starts at 6.10) is : As
>> long as the WG is copied on my AD review comments and proposed changes
>> (which they have been), then the WG has the opportunity to comment or
>> object to the proposed changes if they wish, and lack of comment from the
>> WG is taken as a tacit acceptance of the proposed changes.
>>
>>
>>
>> Given this, I think that the authors can apply the mark ups based on the
>> agreements below (and my original nits), republish, and then hopefully we
>> should be ready to progress this to IETF LC.
>>
>>
>>
>> Regards,
>> Rob
>>
>>
>>
>>
>>
>> *From:* Andy Bierman <andy@yumaworks.com>
>> *Sent:* 05 March 2021 18:46
>> *To:* Rob Wilton (rwilton) <rwilton@cisco.com>
>> *Cc:* NetMod WG Chairs <netmod-chairs@ietf.org>; joel jaeggli <
>> joelja@gmail.com>; draft-ietf-netmod-nmda-diff.all@ietf.org;
>> netmod@ietf.org
>> *Subject:* Re: AD review of draft-ietf-netmod-nmda-diff-07
>>
>>
>>
>>
>>
>>
>>
>> On Fri, Mar 5, 2021 at 10:18 AM Rob Wilton (rwilton) <rwilton@cisco.com>
>> wrote:
>>
>> Hi Andy,
>>
>>
>>
>> I’m not sure which one you think is s a design change:  Do you mean issue
>> 3 or issue 4 below?
>>
>>
>>
>> I see that my response to issue 4 may not have been clear, so to clarify:
>>
>>
>>
>> By “okay”, I meant, that I am okay with how it is written in the current
>> draft.  My presumption is that this could be addressed as a future version
>> of the module if this turns out be an issue, or vendors can define their
>> own augmentation if needed.
>>
>>
>>
>> If you think issue 3 is a design change that requires WG consensus that I
>> will leave it to the WG chairs to decide if they wish to issue a consensus
>> call for it.
>>
>>
>>
>>
>>
>>
>>
>> The change:
>>
>>
>>
>>    Current: default is to include origin attributes and client adds
>> exclude-origin leaf to turn this off
>>
>>    Proposed: default is to exclude origin attributes and client adds
>> report-origin leaf to turn this on
>>
>>     Also, report-origin has an if-feature because origin support in NMDA
>> is optional.
>>
>>
>>
>> I have no objections to this proposal.
>>
>> My point all along has been that this is not my decision to make, it is a
>> WG decision.
>>
>> It does not seem that there are any objections to making this change.
>>
>>
>>
>>
>>
>> Regards,
>>
>> Rob
>>
>>
>>
>>
>>
>> Andy
>>
>>
>>
>>
>>
>> *From:* Andy Bierman <andy@yumaworks.com>
>> *Sent:* 05 March 2021 16:36
>> *To:* Rob Wilton (rwilton) <rwilton@cisco.com>
>> *Cc:* joel jaeggli <joelja@gmail.com>;
>> draft-ietf-netmod-nmda-diff.all@ietf.org; netmod@ietf.org
>> *Subject:* Re: AD review of draft-ietf-netmod-nmda-diff-07
>>
>>
>>
>>
>>
>>
>>
>> On Fri, Mar 5, 2021 at 5:58 AM Rob Wilton (rwilton) <rwilton@cisco.com>
>> wrote:
>>
>> Hi Andy, authors,
>>
>>
>>
>>
>>
>>
>>
>> I think you mean to address this to the WG since the redesign issues need
>> WG approval.
>>
>> I have no objections to any changes.
>>
>>
>>
>>
>>
>> Andy
>>
>>
>>
>> Sorry for the long delay in replying.
>>
>>
>>
>> Please see [RW] inline below …
>>
>>
>>
>>
>>
>> *From:* Andy Bierman <andy@yumaworks.com>
>> *Sent:* 30 October 2020 01:43
>> *To:* joel jaeggli <joelja@gmail.com>
>> *Cc:* Rob Wilton (rwilton) <rwilton@cisco.com>;
>> draft-ietf-netmod-nmda-diff.all@ietf.org; netmod@ietf.org
>> *Subject:* Re: AD review of draft-ietf-netmod-nmda-diff-07
>>
>>
>>
>>
>>
>>
>>
>> On Thu, Oct 29, 2020 at 6:09 PM joel jaeggli <joelja@gmail.com> wrote:
>>
>> Rob,
>>
>>
>>
>> These seem like reasonable suggestions.
>>
>>
>>
>> Lets see what the authors say.
>>
>>
>>
>> Thanks for this
>>
>> joel
>>
>>
>>
>> On Thu, Oct 29, 2020 at 6:47 AM Rob Wilton (rwilton) <rwilton@cisco.com>
>> wrote:
>>
>> Hi,
>>
>> Here is my AD review for draft-ietf-netmod-nmda-diff-07.  Apologies for
>> the delay.
>>
>> Thank you for writing this document, I think that it is useful, and looks
>> like it is in good shape.
>>
>>
>> Main comments:
>>
>> 1. Should there be any text about how to find out what datastores are
>> supported by a device?  E.g., pointing them to either YANG library, or
>> protocol specific mechanisms in the case of RESTCONF.
>>
>>
>>
>> Do you have a section in mind and suggested text?
>>
>> *[RW] *
>>
>> *Perhaps somewhere in section 4, either as part of the description of
>> source, or perhaps before the parameters are described.*
>>
>>
>>
>> *Proposed text:*
>>
>> *“A client can discover which datastores a server supports by reading
>> YANG library [RFC 8525] from the operational state datastore.”*
>>
>>
>>
>>
>>
>>
>>
>> 2. It might be helpful to add a comment about potential issues that could
>> arise by comparing <running> to <operational>, i.e., additional differences
>> could be reported due to inactive configuration and template processing
>> between <running> and <operational>.
>>
>>
>>
>> Do you have a section in mind and suggested text?
>>
>> You mean if there are differences between <running> and <intended>
>>
>> then a diff between <running> and <operational> will not be the same
>>
>> as a diff between <intended> and <operational>.?
>>
>>
>>
>> *[RW] *
>>
>> *My main concern is that if you have template expansion then comparing
>> <running> and <operational> may not really give a meaningful comparison,
>> since <running> is pre-template expansion, and <operational> (and
>> <intended>) are both post template expansion.*
>>
>>
>>
>> *I would suggest putting some text in section 4 or perhaps the YANG
>> module.*
>>
>>
>>
>> *Perhaps some text, something like: *
>>
>>
>>
>> *  “Clients should to be aware that comparing <running> to <operational>
>> will report differences due to any configuration transformation (e.g.,
>> inactive configuration, or the expansion of templates) between the
>> <running> and <intended> datastores.  In these scenarios, clients may get a
>> more useful result by comparing the <intended> and <operational> datastores
>> instead.”*
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> 3. I would prefer if 'exclude=origin' was in the reverse sense and
>> perhaps called 'report-origin' instead.  With the reverse sense it seems to
>> be safer if new datastores are defined, where otherwise the behaviour could
>> end being under specified.
>>
>>
>>
>>
>>
>> IMO the WG already designed the features so if the functional
>> requirements have changed
>>
>> then the draft should go back to the WG for changes and new WG consensus
>> calls.
>>
>> *[RW] *
>>
>>
>>
>> *I don’t see this as really changing the functional requirements, but
>> just changing the default sense and name of an API parameter.  Although,
>> given my comments below “with-origin” might be better than “report-origin”.*
>>
>>
>>
>> *In RFC 8526, the “with-origin” parameter is off by default, and origin
>> metadata is only included when the parameter is included.  This keyword is
>> also under a feature.*
>>
>>
>>
>> *So, changing the parameter name to “with-origin” and putting it under
>> ”if-feature ietf-netconf-nmda:origin”, and making the default off, would
>> make the definition more consistent with RFC 8526.*
>>
>>
>>
>>
>>
>>
>> 4. Should there be an option to filter on origin metadata?  E.g., only
>> include values that come from intended.  Otherwise, things like IP
>> addresses learned from DHCP may always turn up as differences.
>>
>>
>>
>> IMO the WG already designed the features so if the functional
>> requirements have changedthen the draft should go back to the WG for
>> changes and new WG consensus calls.
>>
>>
>>
>> *[RW] *
>>
>>
>>
>> *Okay.*
>>
>>
>>
>> *Regards,*
>>
>> *Rob*
>>
>>
>>
>>
>>
>>
>> 5. I'm not that keen on the "Possible Future Extensions" section of an
>> RFC.  Personally, I would prefer that this section is deleted, but if you
>> wish to retain it, then please can you move it to an appendix.
>>
>>
>>
>> OK with me to remove it
>>
>>
>>
>>
>>
>>
>>
>> Andy
>>
>>
>>
>>
>>
>>
>> I've also included some minor comments inline below, and some nits at the
>> end:
>>
>>     Abstract
>>
>>        This document defines an RPC operation to compare management
>>        datastores that comply with the NMDA architecture.
>>
>> The abstract is perhaps somewhat terse.  Perhaps:
>>
>>     This document defines a YANG RPC operation to compare the
>>     contents of network management datastores that comply with
>>     the NMDA architecture and return the differences in the
>>     YANG-Patch format.
>>
>>
>>     1.  Introduction
>>
>>        The revised Network Management Datastore Architecture (NMDA)
>>        [RFC8342] introduces a set of new datastores that each hold YANG-
>>        defined data [RFC7950] and represent a different "viewpoint" on the
>>        data that is maintained by a server.  New YANG datastores that are
>>        introduced include <intended>, which contains validated
>> configuration
>>        data that a client application intends to be in effect, and
>>        <operational>, which contains at least conceptually operational
>> state
>>        data (such as statistics) as well as configuration data that is
>>        actually in effect.
>>
>> I would suggest deleting "at least conceptually", since the <operational>
>> datastore does contain all operational state, but it may be implemented
>> as a virtual construct that spans multiple nodes (e.g., linecards) and
>> processes.
>>
>>
>>        NMDA introduces in effect a concept of "lifecycle" for management
>>        data, allowing to clearly distinguish between data that is part of
>> a
>>        configuration that was supplied by a user, configuration data that
>>        has actually been successfully applied and that is part of the
>>        operational state, and overall operational state that includes both
>>        applied configuration data as well as status and statistics.
>>
>> "allowing to clearly distinguish" => distinguishing"
>> "status and statistics" => "status information and statistics"
>>
>>
>>        As a result, data from the same management model can be reflected
>> in
>>        multiple datastores.  Clients need to specify the target datastore
>> to
>>        be specific about which viewpoint of the data they want to access.
>>        This way, an application can differentiate whether they are (for
>>        example) interested in the configuration that has been applied and
>> is
>>        actually in effect, or in the configuration that was supplied by a
>>        client and that is supposed to be in effect.
>>
>> Perhaps reword the last sentence to match the logical data flow in the
>> server:
>>
>>    For example, a client application can differentiate whether they are
>>    interested in the configuration supplied to a server and that is
>>    supposed to be in effect, or the configuration that has been applied
>> and is
>>    actually in effect on the server.
>>
>>
>>        When configuration that is in effect is different from
>> configuration
>>        that was applied, many issues can result.  It becomes more
>> difficult
>>        to operate the network properly due to limited visibility of actual
>>        status which makes it more difficult to analyze and understand what
>>        is going on in the network.  Services may be negatively affected
>> (for
>>        example, breaking a service instance resulting in service is not
>>        properly delivered to a customer) and network resources be
>>        misallocated.
>>
>> Perhaps change "actual status" to "actual operational status".
>>
>> I also suggest changing the last sentence to:
>>
>>     Services may be negatively affected (e.g., degrading or breaking a
>> customer service) or network resources may be misallocated.
>>
>>
>>         3. Definitions:
>>
>> It should probably define that <intended>, <operational>, (and perhaps
>> <running>) are used to indicate names of datastores.
>>
>> It should also explain that <compare> is used as the name of a YANG RPC.
>>
>>
>>     4.  Data Model Overview
>>
>>        At the core of the solution is a new management operation,
>> <compare>,
>>        that allows to compare two datastores for the same data.
>>
>> Suggest rewording this first sentence to:
>>
>>   The core of the solution is a new management operation, <compare>,
>>   that compares the data tree contents of two datastores.
>>
>>        o  target: The target identifies the datastore to compare against
>> the
>>           source.
>>
>> Suggest adding an example ", e.g., <operational>."
>>
>>        o  filter-spec: This is a choice between different filter
>> constructs
>>           to identify the portions of the datastore to be retrieved.  It
>>           acts as a node selector that specifies which data nodes are
>> within
>>           the scope of the comparison and which nodes are outside the
>> scope
>>
>>