Hm, OK. So this is now sounding more like a “hold for document update” erratum 
which is our vehicle for saying “the spec could have been clearer, here is some 
improved text, maybe use this if you do a bis”.

I can verify it as HFDU with an updated description — if we have some 
agreed-upon text.

—John

> On Feb 13, 2023, at 4:52 PM, Dave Katz <[email protected]> wrote:
> 
> The intent of the diag field is to leave a breadcrumb behind about what 
> caused the last session failure, so that humans and/or fault analysis can try 
> to guess what happened.  If the session comes back quickly, overwriting the 
> diag on the transition to UP will wipe out that information.
> 
> So I actually am changing my mind on this and would oppose the change.  The 
> erratum, to the extent that it exists is actually in the description of the 
> field, which should say (in effect) “the reason for the most recent change in 
> the local session state except for going Up because we know why we did that”, 
> or something.  But the normative text is sprinkled throughout where the spec 
> calls out when to set the local diag value (which is always copied to the 
> protocol packet) and that does not need to change.
> 
> Thanks for making me think twice, er three times, or something.
> 
> —Dave
> 
>> On Feb 13, 2023, at 6:06 AM, John Scudder <[email protected]> wrote:
>> 
>> I guess it hinges on whether the reinitialization happens when you 
>> transition out of Down, or into Up. As the erratum is written now it’s when 
>> you transition into Up, which appears to make sense, and applies whether the 
>> transition is from Down or from Init. But I’ll wait a little longer for any 
>> further discussion before verifying the erratum. 
>> 
>> —John
>> 
>>> On Feb 13, 2023, at 4:37 AM, Gļebs Ivanovskis 
>>> <[email protected]> wrote:
>>> 
>>> 
>>> Hi!
>>> 
>>> Wouldn't it make sense to re-initialize bfd.LocalDiag when transitioning to 
>>> Init state as well?
>>> 
>>> Section 6.8.6 describes a case when bfd.SessionState goes from Down to Init:
>>> 
>>>          If bfd.SessionState is Down
>>>              If received State is Down
>>>                  Set bfd.SessionState to Init
>>> 
>>> Best regards,
>>> Glebs
>>> 
>>> 
>>> On 08.02.23 19:58, John Scudder wrote:
>>>> Hi Everyone,
>>>> 
>>>> I plan to verify this in the near future (let’s say, Monday Feb 13) unless 
>>>> anyone objects. 
>>>> 
>>>> Thanks,
>>>> 
>>>> —John
>>>> 
>>>> 
>>>>> On Nov 6, 2022, at 4:27 AM, RFC Errata System <[email protected]>
>>>>> wrote:
>>>>> 
>>>>> The following errata report has been submitted for RFC5880,
>>>>> "Bidirectional Forwarding Detection (BFD)".
>>>>> 
>>>>> --------------------------------------
>>>>> You may review the report below and at:
>>>>> 
>>>>> https://urldefense.com/v3/__https://www.rfc-editor.org/errata/eid7240__;!!NEt6yMaO-gk!DSW_aH2n7cYViXw08rr41mmdkcad5rzUky6aMWE1XW-uhZqqdIELlYuLQ20Sw8Z1cTiyiqHvd7VyqUJIsm_Lmg$
>>>>> 
>>>>> 
>>>>> --------------------------------------
>>>>> Type: Technical
>>>>> Reported by: Jeffrey Haas 
>>>>> <[email protected]>
>>>>> 
>>>>> 
>>>>> 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
>>>>> --------------
>>>>> [Proposed 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).  It MUST also be re-initialized to zero
>>>>>     (No Diagnostic) when the local session state transitions to Up.
>>>>> 
>>>>> 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.  However, it doesn't define under what 
>>>>> conditions it should be re-initialized to zero.
>>>>> 
>>>>> One possible place where it may be reinitialized is when the session 
>>>>> transitions back to Up, indicating that prior issues may have been 
>>>>> cleared.
>>>>> 
>>>>> Instructions:
>>>>> -------------
>>>>> This erratum is currently posted as "Reported". If necessary, please
>>>>> use "Reply All" to discuss whether it should be verified or
>>>>> rejected. When a decision is reached, the verifying party
>>>>> can log in to change the status and edit the report, if necessary.
>>>>> 
>>>>> --------------------------------------
>>>>> RFC5880 (draft-ietf-bfd-base-11)
>>>>> --------------------------------------
>>>>> 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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