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

From: Robert Wilton via Datatracker <[email-masked]>
Date: Thu, 07 Apr 2022 04:43:31 -0700

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

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DISCUSS:
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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