Re: [core] Éric Vyncke's No Objection on draft-ietf-core-hop-limit-06: (with COMMENT)

<mohamed.boucadair@orange.com> Tue, 15 October 2019 08:23 UTC

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From: <mohamed.boucadair@orange.com>
To: "Eric Vyncke (evyncke)" <evyncke@cisco.com>, The IESG <iesg@ietf.org>
CC: "draft-ietf-core-hop-limit@ietf.org" <draft-ietf-core-hop-limit@ietf.org>, Jaime Jimenez <jaime@iki.fi>, "core-chairs@ietf.org" <core-chairs@ietf.org>, "core@ietf.org" <core@ietf.org>
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Date: Tue, 15 Oct 2019 08:23:44 +0000
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Hi Eric, 

Please see inline.

Cheers,
Med

> -----Message d'origine-----
> De : Eric Vyncke (evyncke) [mailto:evyncke@cisco.com]
> Envoyé : lundi 14 octobre 2019 16:20
> À : BOUCADAIR Mohamed TGI/OLN; The IESG
> Cc : draft-ietf-core-hop-limit@ietf.org; Jaime Jimenez; core-
> chairs@ietf.org; core@ietf.org
> Objet : Re: Éric Vyncke's No Objection on draft-ietf-core-hop-limit-06:
> (with COMMENT)
> 
> Hello Mohamed,
> 
> Thank you for your reply.
> 
> Look inline for EVY> (and feel free to ignore)
> 
> -éric
> 
> On 11/10/2019, 09:59, "mohamed.boucadair@orange.com"
> <mohamed.boucadair@orange.com> wrote:
> 
>     Hi Eric,
> 
>     Thank you for the review.
> 
>     Please see inline.
> 
>     Cheers,
>     Med
> 
>     > -----Message d'origine-----
>     > De : Éric Vyncke via Datatracker [mailto:noreply@ietf.org]
>     > Envoyé : vendredi 11 octobre 2019 08:41
>     > À : The IESG
>     > Cc : draft-ietf-core-hop-limit@ietf.org; Jaime Jimenez; core-
>     > chairs@ietf.org; jaime@iki.fi; core@ietf.org
>     > Objet : Éric Vyncke's No Objection on draft-ietf-core-hop-limit-06:
> (with
>     > COMMENT)
>     >
>     > Éric Vyncke has entered the following ballot position for
>     > draft-ietf-core-hop-limit-06: No Objection
>     >
>     > When responding, please keep the subject line intact and reply to all
>     > email addresses included in the To and CC lines. (Feel free to cut
> this
>     > introductory paragraph, however.)
>     >
>     >
>     > Please refer to https://www.ietf.org/iesg/statement/discuss-
> criteria.html
>     > for more information about IESG DISCUSS and COMMENT positions.
>     >
>     >
>     > The document, along with other ballot positions, can be found here:
>     > https://datatracker.ietf.org/doc/draft-ietf-core-hop-limit/
>     >
>     >
>     >
>     > ---------------------------------------------------------------------
> -
>     > COMMENT:
>     > ---------------------------------------------------------------------
> -
>     >
>     > Thank you for the work put into this document. I have a couple of
> COMMENTs
>     > (that I would appreciate to see a reply of yours) and one NIT.
>     >
>     > Regards,
>     >
>     > -éric
>     >
>     > == DISCUSS ==
>     >
>     > == COMMENTS ==
>     >
>     > -- Section 3 --
>     > C.1) "Because forwarding errors may occur if inadequate Hop-Limit
> values
>     >    are used, proxies at the boundaries of an administrative domain
> MAY
>     >    be instructed to remove or rewrite the value of Hop-Limit carried
> in
>     >    received messages" Isn't this remove all usefulness of the Hop-
> Limit
>     > option ?
> 
>     [Med] This is warranted in the next sentence: "This modification should
> be done with caution in case proxy-forwarded traffic repeatedly crosses the
> administrative domain boundary in a loop and so Hop-Limit detection gets
> broken."
> 
>     Basically, the decision will be deployment-specific. E.g., if the
> boundary proxy is the only proxy to be invoked before reaching the ultimate
> CoAP endpoint, striping the option may be OK.
> 
> EVY> still looks like defeating the whole purpose because how one proxy
> would know FOR SURE that it is the last one?
> 

[Med] This is known to the administrative entity managing the proxy; instructions are then passed to the proxy. Absent such instruction, the default behavior of a proxy is to maintain the option.  

>     >
>     > C.2) table 1, suggest to state the value of the C, U, N, R properties
> 
>     [Med] The option is elective, safe-to-forward, part of the cache, and
> not repeatable. So, none of C, U, N, R is marked with "x" in the table.
> 
> EVY> LoL __ but a little unclear at first sight. Unsure whether other
> documents use a "0" or "." to specify 'not-set' ? My point is that this
> document should really align with others.

[Med] I got that. I confirm that the document is aligned with RFC7252. Will see how to make thing more clear.

>     >
>     > -- Section 4 --
>     > C.3) while I understand why a proxy should not add its own diagnostic
>     > information when packet should become larger than the MTU of the next
> link,
>     > I
>     > wonder what will happen downstream when the MTU will be exceeded...
> 
>     [Med] The behavior of the proxy will take into account the "Path" MTU
> not the link MTU:
> 
>        Note that an
>        intermediate proxy prepends its information only if there is enough
>        space as determined by the Path MTU (Section 4.6 of [RFC7252]).
>                                   ^^^^^^^^
> 
>     With that assumption, I don't see any MTU issue when forwarding the
> packet downstream. No?
> 
> EVY> my bad, I should learn to read...
> 
>     >
>     > C.4) suggest to use normative language (uppercase MAY, MUST, ...)
>     >
> 
>     [Med] We used to have more normative language in that section but
> cleaned it as a result of this WGLC comment:
> 
>     ========
>     > > 3. "To ease debugging and troubleshooting, the CoAP proxy which
>     > > detects a loop SHOULD include its information ... Each intermediate
>     > > proxy involved in relaying a TBA1 (Hop Limit Reached) error message
>     > > SHOULD prepend its own information" - Is it really a protocol
>     > > violation if I want to configure my proxy not to include any
>     > > information?
>     > >
>     >
>     > [Med] It is not a protocol violation if the information is not
> included - hence the SHOULD. However it makes diagnosing the issue more
> difficult.
> 
>     We briefly discussed this in the interim yesterday and came to the
>     conclusion that having a normative requirement here isn't needed. It
>     seems more like a suggestion for a good quality of implementation. I
>     propose to remove any use of KEYWORDs here.
>     ==========
> 
>     > == NITS ==
>     >
>     > -- Section 3 --
>     > N.1) s/if a less value/if a smaller value/ ?
> 
>     [Med] Fixed. Thank you.
> 
>