Re: [Idr] [Technical Errata Reported] RFC4271 (5001)

<bruno.decraene@orange.com> Thu, 20 April 2017 07:24 UTC

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From: <bruno.decraene@orange.com>
To: "Alvaro Retana (aretana)" <aretana@cisco.com>, "John G. Scudder" <jgs@juniper.net>
CC: "idr@ietf.org" <idr@ietf.org>
Thread-Topic: [Technical Errata Reported] RFC4271 (5001)
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Date: Thu, 20 Apr 2017 07:24:33 +0000
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Subject: Re: [Idr] [Technical Errata Reported] RFC4271 (5001)
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> From: bruno.decraene@orange.com  > Sent: Wednesday, April 19, 2017 8:46 PM
> 
 > Alvaro, John, all
 > 
 > I may have one comment. Please see inline.
 > 
 > 
 > > From Alvaro Retana (aretana)  > Sent: Wednesday, April 19, 2017 8:01 PM
 > >
 >  > [Cut the distribution.]
 >  >
 >  > idr WG:
 >  >
 >  > I think this report is a lot clearer than the other one John filed (#5000), so I am going to
 >  > mark this one as “Hold for Document Update” [1].
 >  >
 >  > Just because this report is related to the use of “MAY NOT” I will wait until we resolve the
 >  > other one just in case.
 >  >
 >  > Thanks!
 >  >
 >  > Alvaro.
 >  >
 >  > [1] https://www.ietf.org/iesg/statement/errata-processing.html
 >  >
 >  >
 >  >
 >  > On 4/19/17, 1:40 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=5001
 >  >
 >  > --------------------------------------
 >  > Type: Technical
 >  > Reported by: John Scudder <jgs@juniper.net>;
 >  >
 >  > Section: 5
 >  >
 >  > Original Text
 >  > -------------
 >  >    BGP implementations MUST recognize all well-known attributes.  Some
 >  >    of these attributes are mandatory and MUST be included in every
 >  >    UPDATE message that contains NLRI.  Others are discretionary and MAY
 >  >    or MAY NOT be sent in a particular UPDATE message.
 >  >
 >  >
 >  > Corrected Text
 >  > --------------
 >  >    BGP implementations MUST recognize all well-known attributes.  Some
 >  >    of these attributes are mandatory and MUST be included in every
 >  >    UPDATE message that contains NLRI.  Others are discretionary and
 >  >    sending them in a particular UPDATE message is OPTIONAL.
 > 
 > IMHO, OPTIONAL may not be what was intended.
 > As per RFC 2119 " the adjective "OPTIONAL", mean that an item is
 >    truly optional.  One vendor may choose to include the item because a
 >    particular marketplace requires it or because the vendor feels that
 >    it enhances the product while another vendor may omit the same item."

While the original text is about "well-known" attributes, which in BGP means mandatory to implement. i.e. the opposite of RFC 2119 "OPTIONAL" meaning.

--Bruno
 
 > Here, I think that the original intention was to say that the attribute MAY be sent if
 > appropriate and MAY be omitted if appropriate. IOW, it is _not_ REQUIRED to always send it.
 > 
 > As an example, quickly parsing RFC 4171, it does not seem to indicate whether the
 > LOCAL_PREF attribute is mandatory or discretionary. But given that it is well-known, as per
 > §5, it can only be mandatory or discretionary. Given that it usually does not appear in EBGP
 > session, I would argue that it is not mandatory, hence discretionary. But I don't think that we
 > could say that sending the attribute LOCAL_PREF is OPTIONAL given that RFC 4271
 > mandates its use in IBGP (plus not sending it on some IBGP sessions would create forwarding
 > loops).
 > 
 > I may propose the follow text: Others are discretionary and may or may not be sent in a
 > particular UPDATE message
 > Or: Others are discretionary and are not required to be sent in all UPDATE message
 > 
 > --Bruno
 > 
 >  > 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". In context, it is unlikely the
 >  > reader would be at risk of misinterpreting the text, but nonetheless it's a misuse of RFC
 >  > 2119 terminology and difficult to parse if reading closely.
 >  >
 >  > (The replacement text was suggested by Eric Rosen; thanks.)
 >  >
 >  > 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
 >  >
 >  >
 >  > _______________________________________________
 >  > Idr mailing list
 >  > Idr@ietf.org
 >  > https://www.ietf.org/mailman/listinfo/idr
 > 
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Orange decline toute responsabilite si ce message a ete altere, deforme ou falsifie. Merci.

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