Re: WG Review: NETCONF Data Modeling Language (netmod)

Eric Rescorla <> Tue, 22 April 2008 16:06 UTC

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Date: Tue, 22 Apr 2008 09:10:10 -0700
From: Eric Rescorla <>
Subject: Re: WG Review: NETCONF Data Modeling Language (netmod)
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I object to the formation of this WG with this charter.

While there was a clear sense during the BOF that there was interest
in forming a WG, there was absolutely no consensus on technical
direction. Rather, a number of proposals were presented, but no
strawpoll, hum, or sense of the room was taken, nor, as far as I can
determine, has there been any such consensus call been taken on any
list I'm aware of. This wasn't an accident--the BOF was explicitly
intended only to determine whether some work in this area should
proceed, not to select a technical approach.

I understand that an approach like this was proposed in the OPSAREA
meeting by Chris Newman and then that there was a breakout meeting
where it was discussed further. The minutes don't record any consensus
call on this combined direction (only strawpolls on the individual
proposals), and even if such a consensus call had been held, the
OPSAREA meeting would not be the appropriate place for it: this
discussion needs to happen in either the BOF (to allow cross-area
review) or in the designated WG, when it is formed. 
Accordingly, if this WG is to be formed, the entire section (and
corresponding milestones) which specifies the technology needs to be
removed. Rather, the first work item should be to select a technical


> NETCONF Data Modeling Language (netmod)
> ----------------------------------------
> Last modified: 2008-04-10
> Current Status: Proposed Working Group
> Chair(s): 
> Operations and Management Area Director(s):
> Dan Romascanu <dromasca at>
> Ronald Bonica rbonica at
> Mailing Lists:
> General Discussion: ngo at
> Description:
> The NETCONF Working Group has completed a base protocol to be
> used for configuration management.  However, the NETCONF protocol
> does not include a standard content layer.  The specifications do
> not include a modeling language or accompanying rules that can be
> used to model the management information that is to be configured
> using NETCONF. This has resulted in inconsistent syntax and
> interoperability problems. The purpose of NETMOD is to support
> the ongoing development of IETF and vendor-defined data models
> for NETCONF.
> NETMOD's requirements are drawn from the RCDML requirements draft
> (draft-presuhn-rcdml) and documents referenced therein.

> The WG will define a "human-friendly" modeling language defining
> the semantics of operational data, configuration data,
> notifications, and operations.  This language will focus on
> readability and ease of use.  This language must be able to serve
> as the normative description of NETCONF data models.  The WG will
> use YANG (draft-bjorklund-yang) as its starting point for this
> language.
> Language abstractions that facilitate model extensibility and
> reuse have been identified as a work area and will be considered
> as a work item or may be integrated into the YANG document based
> on WG consensus.
> The WG will define a canonical mapping of this language to
> NETCONF XML instance documents, the on-the-wire format of
> YANG-defined XML content.  Only data models defined in YANG will
> have to adhere to this on-the-wire format.
> In order to leverage existing XML tools for validating NETCONF
> data in various contexts and also facilitate exchange of data
> models and schemas with other IETF working groups, the WG will
> define standard mapping rules from YANG to the DSDL data modeling
> framework (ISO/IEC 19757) with additional annotations to preserve
> semantics.
> The initial YANG mapping rules specifications are expressly defined for
> NETCONF modeling.  However, there may be future areas of
> applicability beyond NETCONF, and the WG must provide suitable
> language extensibility mechanisms to allow for such future work.
> The NETMOD WG will only address modeling NETCONF devices and the
> language extensibility mechanisms.  Any application of YANG to
> other protocols is future work.
> The WG will consult with the NETCONF WG to ensure that NETMOD's
> decision do not conflict with planned work in NETCONF (e.g.,
> locking, notifications).
> While it is desirable to provide a migration path from existing
> MIB modules to YANG data models (modules), it is not a
> requirement to provide full compatibility between SMIv2 and YANG.
> The Working Group will determine which constructs (e.g., conformance
> statements) are not relevant for translation from SMIv2 to YANG. YANG is
> also permitted to introduce constructs that cannot be expressed in SMIv2.
> However, all basic types that can be represented in SMIv2 must be
> expressible in YANG.
> Initial deliverables are below.  The working group may choose to
> combine multiple deliverables into a single document where deemed
> appropriate.
> 1. An architecture document explaining the relationship
> between YANG and its inputs and outputs. (informational)
> 2. The YANG data modeling language and semantics (proposed
> standard)
> 3. Mapping rules of YANG to XML instance data in NETCONF
> (proposed standard)
> 4. YIN, a semantically equivalent fully reversible mapping to an
> XML-based syntax for YANG.  YIN is simply the data model in an XML syntax
> that can be manipulated using existing XML tools (e.g., XSLT) (proposed
> standard)
> 5. Mapping rules of YANG to DSDL data modeling framework (ISO/IEC
> 19757), including annotations for DSDL to preserve top-level
> semantics during translation (proposed standard).
> 6. A standard type library for use by YANG (proposed standard)
> Goals and Milestones:
> Jun 2008 - All _individual_ drafts available that will be used as
> input into the WG documents (draft-bjorklund-yang, architecture
> draft, YIN draft, YANG standard library draft, DSDL mapping rules
> draft)
> Aug 2008 - Initial set of WG drafts: architecture, YANG, YIN,
> YANG standard library, DSDL mapping rules (if there is one/more
> individual draft), based on WG decisions in Dublin
> Sep 2008 - Initial DSDL mapping rules document
> Oct 2008 - 01 of YANG, DSDL, architecture, YIN, and standard
> library draft.  If split out, -00 of on-the-wire XML draft.
> Feb 2009 - WGLC for architecture doc
> Mar 2009 - Submit the architecture doc to the IESG for
> publication as an Informational RFC
> Aug 2009 - WGLC for YANG, YIN, XML on-the-wire (if split out),
> YANG standard library, DSDL mapping rules
> Sep 2009 - Submit YANG, YIN, XML on-the-wire (if split out), YANG
> standard library, DSDL mapping rules to the IESG for publication as a
> Proposed Standard
> _______________________________________________
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