Re: [Idr] [Technical Errata Reported] RFC4271 (5000)

"Acee Lindem (acee)" <acee@cisco.com> Wed, 19 April 2017 19:32 UTC

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From: "Acee Lindem (acee)" <acee@cisco.com>
To: "Alvaro Retana (aretana)" <aretana@cisco.com>, "idr@ietf.org" <idr@ietf.org>
Thread-Topic: [Idr] [Technical Errata Reported] RFC4271 (5000)
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Date: Wed, 19 Apr 2017 19:32:17 +0000
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Subject: Re: [Idr] [Technical Errata Reported] RFC4271 (5000)
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Hi Alvaro, 

I would vote for John’s suggested option b. As John stated, this
disambiguates the statement in the context of RFC 2119’s definition of
“MAY”. From an implementation standpoint, I would see any other
interpretation as a bug.

Thanks,
Acee 



On 4/19/17, 1:56 PM, "Idr on behalf of Alvaro Retana (aretana)"
<idr-bounces@ietf.org on behalf of aretana@cisco.com> wrote:

>[Cutting the distribution a little.]
>
>[John: thanks for filing this report.]
>
>idr WG:
>
>As you know, changes to rfc4271 should be handled with care.  And this
>case is no exception.
>
>Even if “MAY NOT” is not an rfc2119 keyword as “MAY”, “MUST NOT”, and
>others are, it doesn’t give me a great feeling to change it for one that
>is – among other things because the meaning of “MAY” and “MUST” is so
>different.  Of course, making me feel good is not the purpose of rfc2119…
>;-)
>
>Having said that, it is important that rfc4271 faithfully represent what
>the WG intended.  In this case, even though John didn’t say it
>explicitly, I would agree with him in considering that implementers may
>have already interpreted the text with the intent to not use the routes
>further.
>
>I would like to get input from the WG as to the best way to handle this
>report.  I would specially like to hear from implementers, but all input
>is welcome.
>
>The options are:
>
>a. s/MAY NOT/may not
>b. s/MAY NOT/MUST NOT
>c. Rejecting the report.
>d. Something else…
>
>I will wait at least a week before proceeding.
>
>Thanks!
>
>Alvaro.
>
>
>
>On 4/19/17, 1:37 PM, "RFC Errata System" <rfc-editor@rfc-editor.org>
>wrote:
>
>The following errata report has been submitted for RFC4271,
>"A Border Gateway Protocol 4 (BGP-4)".
>
>--------------------------------------
>You may review the report below and at:
>http://www.rfc-editor.org/errata_search.php?rfc=4271&eid=5000
>
>--------------------------------------
>Type: Technical
>Reported by: John Scudder <jgs@juniper.net>
>
>Section: 9.1.1
>
>Original Text
>-------------
>      If the route is learned from an external peer, then the local BGP
>      speaker computes the degree of preference based on preconfigured
>      policy information.  If the return value indicates the route is
>      ineligible, the route MAY NOT serve as an input to the next phase
>      of route selection; otherwise, the return value MUST be used as
>      the LOCAL_PREF value in any IBGP readvertisement.
>
>
>Corrected Text
>--------------
>      If the route is learned from an external peer, then the local BGP
>      speaker computes the degree of preference based on preconfigured
>      policy information.  If the return value indicates the route is
>      ineligible, the route MUST NOT serve as an input to the next phase
>      of route selection; otherwise, the return value MUST be used as
>      the LOCAL_PREF value in any IBGP readvertisement.
>
>
>Notes
>-----
>The original text uses "MAY NOT" capitalized as if it were an RFC 2119
>keyword. However, RFC 2119 does not have any defined meaning for "MAY
>NOT". If a reader were to interpret this text as suggesting it is
>optional -- meaning, in effect, "the route MAY serve as an input to the
>next phase of route selection" -- that would be wrong and potentially
>problematic.
>
>The minimal correction would be to use lower-case "may not", which makes
>the proper meaning reasonably clear. However, the English construct "may
>not" is notoriously ambiguous, therefore the proposed correction is "MUST
>NOT".
>
>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.
>
>--------------------------------------
>RFC4271 (draft-ietf-idr-bgp4-26)
>--------------------------------------
>Title               : A Border Gateway Protocol 4 (BGP-4)
>Publication Date    : January 2006
>Author(s)           : Y. Rekhter, Ed., T. Li, Ed., S. Hares, Ed.
>Category            : DRAFT STANDARD
>Source              : Inter-Domain Routing
>Area                : Routing
>Stream              : IETF
>Verifying Party     : IESG
>
>
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