Re: [Lsr] Proposed Errata for RFCs 8919/8920

[[e-mail]]

Les, Peter,

Thank you for agreeing to clarify the sentence and for the effort put in proposing a new text.

Proposed text looks much better to me. I particularly like the either MUST or MUST NOT statement.

I have one comment.
In the RFC, the term "advertisement" is used to refer both to sub-TLV [1] and to ASLA attribute [2]
[1] https://www.rfc-editor.org/rfc/rfc8919.html#name-legacy-advertisements
[2] https://www.rfc-editor.org/rfc/rfc8919.html#name-advertising-application-spe

As such, I would have a slight preference to be explicit about the type of advertisement which is meant. Especially since Gunter, an AD and myself raised that exact point, and that OSPF and IS-IS did not seemed aligned on this.

I would propose the following change in RFC 8919 section 4.2 & RFC 8920 section 5
OLD: Such advertisements MUST
NEW: Such link attribute advertisements MUST

(I'm aware that the previous sentence starts with "Link attributes MAY be advertised", which in general should be a clear enough reference. But since we are clarifying, IMHO the more straightforward the clarification, the better, especially for the OSPF document which seemed to use the alternative understanding)


I definitely agree that this wording affects interoperability and must be fixed.
I'm not taking position (and don't care) whether an errata is the appropriate way. I'm happy to leave this to the chairs and AD. But my understanding is that if the errata is not classified as "Verified", then we'll need a bis document.

Thanks,
Regards,
--Bruno

From: Les Ginsberg (ginsberg) [mailto:[e-mail]]
Sent: Tuesday, June 15, 2021 5:25 PM
To: [e-mail]
Cc: DECRAENE Bruno INNOV/NET <[e-mail]>; Van De Velde, Gunter (Nokia - BE/Antwerp) <[e-mail]>
Subject: Proposed Errata for RFCs 8919/8920


Folks -



Recent discussions on the list have highlighted some unintentional ambiguity in how ASLA advertisements are to be used. Please see https://mailarchive.ietf.org/arch/msg/lsr/prSLJDkMUnHm6h7VuCdn_Q7-1vg/



The following proposed Errata address this ambiguity and aligns language in the two RFCs.



We welcome comments on the proposed Errata before officially filing them.



  Les and Peter


Errata Explanation

Both RFC 8919 and RFC 8920 define advertising link attributes with zero length Standard Application Bit Mask (SABM) and zero length User Defined Application Bit Mask (UDABM)
as a means of advertising link attributes that can be used by any application. However, the text uses the word "permitted", suggesting that the use of such advertisements is "optional".
Such an interpretation could lead to interoperability issues and is not what was intended.

The replacement text below makes explicit the specific conditions when such advertisements MUST be used and the specific conditions under which they MUST NOT be used.

RFC 8919 Section 4.2:

OLD

"If link attributes are advertised associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications,
then any standard application and/or any user-defined application is permitted to use that set of link attributes so long as there is not another set of attributes
advertised on that same link that is associated with a non-zero-length Application Identifier Bit Mask with a matching Application Identifier Bit set."

NEW

"Link attributes MAY be advertised associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications.
Such advertisements MUST be used by standard applications and/or user defined applications when no link attribute advertisements with a non-zero-length
Application Identifier Bit Mask and a matching Application Identifier Bit set are present for a given link. Otherwise, such advertisements MUST NOT be used."

RFC 8919 Section 6.2

OLD

"Link attribute advertisements associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications are usable
by any application, subject to the restrictions specified in Section 4.2. If support for a new application is introduced on any node in a network in the presence of such
advertisements, these advertisements are permitted to be used by the new application. If this is not what is intended, then existing advertisements MUST be readvertised
with an explicit set of applications specified before a new application is introduced."


NEW

"Link attribute advertisements associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications are usable
by any application, subject to the restrictions specified in Section 4.2. If support for a new application is introduced on any node in a network in the presence of such
advertisements, the new application will use these advertisements, when the aforementioned restrictions are met. If this is not what is intended, then existing
advertisements MUST be readvertised with an explicit set of applications specified before a new application is introduced."



RFC 8920 Section 5

OLD

"If link attributes are advertised with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications,
then any standard application and/or any user-defined application is permitted to use that set of link attributes. If support for a new application
is introduced on any node in a network in the presence of such advertisements, these advertisements are permitted to be used by the new
application. If this is not what is intended, then existing advertisements MUST be readvertised with an explicit set of applications specified
before a new application is introduced.

An application-specific advertisement (Application Identifier Bit Mask with a matching Application Identifier Bit set) for an attribute MUST
always be preferred over the advertisement of the same attribute with the zero-length Application Identifier Bit Masks for both standard
applications and user-defined applications on the same link."

NEW

"Link attributes MAY be advertised associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications.
Such advertisements MUST be used by standard applications and/or user defined applications when no link attribute advertisements with a non-zero-length
Application Identifier Bit Mask and a matching Application Identifier Bit set are present for a given link. Otherwise, such advertisements MUST NOT be used."



RFC 8920 New Section between 12.1 and 12.2. Current sections following this new section will need to be renumbered.


12.2 Use of Zero-Length Application Identifier Bit Masks

"Link attribute advertisements associated with zero-length Application Identifier Bit Masks for both standard applications and user-defined applications are usable
by any application, subject to the restrictions specified in Section 5. If support for a new application is introduced on any node in a network in the presence of such
advertisements, the new application will use these advertisements, when the aforementioned restrictions are met. If this is not what is intended, then existing
advertisements MUST be readvertised with an explicit set of applications specified before a new application is introduced."





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