Re: [mpls] [Technical Errata Reported] RFC8960 (7059)

From: mpls <mpls-bounces@ietf.org> on behalf of RFC Errata System <rfc-editor@rfc-editor.org>
Sent: 29 July 2022 12:22

The following errata report has been submitted for RFC8960,
"A YANG Data Model for MPLS Base".

--------------------------------------
You may review the report below and at:
https://www.rfc-editor.org/errata/eid7059

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Type: Technical
Reported by: Jan Lindblad <jlindbla@cisco.com>

<tp>

I think that Jan is right in the sense that

- the author did not understand the YANG that they specified (or at least the XML part) 
- it renders the when clause more or less meaningless

It is also very widespread across WG and I-D/RFC which makes fixing it a challenge (a bit like having or not having zone in an ip-address type).

It is also a technical change to what the WG endorsed at the time.

Challenging.

Tom Petch

Section: 2.5

Original Text
-------------
        augment "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/"
              + "rt:next-hop/rt:next-hop-options/rt:simple-next-hop" {
          description
            "Augments the 'simple-next-hop' case in IP unicast routes.";
          uses nhlfe-single-contents {
            when "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route"
               + "/mpls:mpls-enabled = 'true'";
          }
        }

Corrected Text
--------------
        augment "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/"
              + "rt:next-hop/rt:next-hop-options/rt:simple-next-hop" {
          description
            "Augments the 'simple-next-hop' case in IP unicast routes.";
          uses nhlfe-single-contents {
            when "../../../mpls:mpls-enabled = 'true'";
          }
        }

Notes
-----
The original YANG statements make the "uses" statement apply to all rt:rib and all rt:route instances as soon as there is at least one instance that has mpls:mpls-enabled set to true. I suspect this is not the author's intent.

The corrected YANG statements make the "uses" statement only apply to the specific route instances that have mpls:mpls-enabled set to true. There are also other ways to fix this issue.

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--------------------------------------
RFC8960 (draft-ietf-mpls-base-yang-17)
--------------------------------------
Title               : A YANG Data Model for MPLS Base
Publication Date    : December 2020
Author(s)           : T. Saad, K. Raza, R. Gandhi, X. Liu, V. Beeram
Category            : PROPOSED STANDARD
Source              : Multiprotocol Label Switching
Area                : Routing
Stream              : IETF
Verifying Party     : IESG

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