Re: [Teas] Robert Wilton's Discuss on draft-ietf-teas-gmpls-signaling-smp-11: (with DISCUSS)

[Jeong-dong Ryoo <[e-mail]>]

Hi, Robert.


Thank you for your review and comments. 

Indeed, it is possible that the current text may lead to confusion and ambiguity.

The co-authors of this draft would like to revise the draft as per your first suggestion. We want to keep the "If 0x20 (SMP), the N bit MUST be set to 1." sentence, since it can be helpful to have an explicit statement in the part that defines the values of the message bits.
 
We will upload a revised text shortly.


Best regards,

Jeong-dong (on behalf of the co-authors)



-----Original Message-----
From:  "Robert Wilton via Datatracker" <[e-mail]>
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Sent:  2022-04-07 (목) 20:43:42 (UTC+09:00)
Subject: Robert Wilton's Discuss on draft-ietf-teas-gmpls-signaling-smp-11: (with DISCUSS)

Robert Wilton has entered the following ballot position for
draft-ietf-teas-gmpls-signaling-smp-11: Discuss

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----------------------------------------------------------------------
DISCUSS:
----------------------------------------------------------------------

Thanks for this document, and sorry for the late discuss, which should
hopefully be trivial to fix.

   Notification (N): 1 bit

      When set to 1, this bit indicates that the control plane message
      exchange is only used for notification during protection
      switching.  When set to 0 (default), it indicates that the control
      plane message exchanges are used for protection-switching
      purposes.  The N bit is only applicable when the LSP Protection
      Type Flag is set to 0x04 (1:N Protection with Extra- Traffic),
      0x08 (1+1 Unidirectional Protection), 0x10 (1+1 Bidirectional
      Protection), or 0x20 (Shared Mesh Protection).  If 0x20 (SMP), the
      N bit MUST be set to 1.  The N bit MUST be set to 0 in any other
      case.

I think that the way that this RFC4872 text has been updated makes this text
unclear/ambiguous.

Specifically, I think that somebody could reasonably interpret this as saying
that the N bit is set to 1 for SMP, and otherwise it must always be set to 0,
but I don't think that is the intention.  So please can this be clarified.

One fix could be to swap the order of the last 2 sentences.  E.g.,

      or 0x20 (Shared Mesh Protection).  The N bit MUST
      be set to 0 in any other case. If 0x20 (SMP), the
      N bit MUST be set to 1.

Alternatively, I think that you could possibly just remove the "If 0x20 (SMP),
the N bit MUST be set to 1." and instead rely on the text in 5.2/5.3, (perhaps
strengthening with RFC 2119 language if required).

Regards,
Rob