The following errata report has been held for document update 
for RFC5880, "Bidirectional Forwarding Detection (BFD)". 

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You may review the report below and at:
https://www.rfc-editor.org/errata/eid7240

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Status: Held for Document Update
Type: Technical

Reported by: Jeffrey Haas <[email protected]>
Date Reported: 2022-11-06
Held by: John Scudder (IESG)

Section: 6.8.1

Original Text
-------------
   bfd.LocalDiag

      The diagnostic code specifying the reason for the most recent
      change in the local session state.  This MUST be initialized to
      zero (No Diagnostic).

Corrected Text
--------------
No proposed changes are offered here. See the notes for further discussion.

Notes
-----
RFC 5880 at various points calls out setting the value of bfd.LocalDiag as part 
of state transitions. The text defining the feature calls for it to be 
initialized to zero. Discussion on the WG mailing list following the filing of 
the initial version of this erratum revealed two things:

First, the text of the RFC is correct, complete, and reflects the authors’ 
intention at the time of writing, which really WAS that the value should only 
be initialized to zero but not reset to zero at any other time. 

Second, by not emphasizing this point, the spec although formally speaking 
unambiguous, left space for implementors to exercise their intuitions and 
creativity. As a result, several implementations are reported to reset this 
value to zero when the session transitions back to Up.

The discussion is archived at 
https://mailarchive.ietf.org/arch/msg/rtg-bfd/yEOx2LTO51zq1he6vChUOVJySqM/ . If 
a new version of RFC 5880 is prepared in the future, this question should be 
reopened as part of that process. It would also be possible to offer a 
standards track document to update RFC 5880 in this respect if WG consensus can 
be found for a new approach. 

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RFC5880 (draft-ietf-bfd-base-11)
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Title               : Bidirectional Forwarding Detection (BFD)
Publication Date    : June 2010
Author(s)           : D. Katz, D. Ward
Category            : PROPOSED STANDARD
Source              : Bidirectional Forwarding Detection
Area                : Routing
Stream              : IETF
Verifying Party     : IESG

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