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

joel jaeggli <> Fri, 30 October 2020 01:09 UTC

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From: joel jaeggli <>
Date: Thu, 29 Oct 2020 18:09:00 -0700
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Subject: Re: [netmod] AD review of draft-ietf-netmod-nmda-diff-07
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These seem like reasonable suggestions.

Lets see what the authors say.

Thanks for this

On Thu, Oct 29, 2020 at 6:47 AM Rob Wilton (rwilton) <>

> 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.
> 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>.
> 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.
> 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.
> 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.
> 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