Re: [Dots] Alissa Cooper's Discuss on draft-ietf-dots-signal-channel-31: (with DISCUSS and COMMENT)

[Benjamin Kaduk <[e-mail]>]

On Fri, May 03, 2019 at 07:17:55AM +0000, Konda, Tirumaleswar Reddy wrote:
> Hi Alissa,
> 
> Please see inline
> 
> From: Dots <[e-mail]> On Behalf Of Alissa Cooper
> Sent: Thursday, May 2, 2019 8:50 PM
> To: [e-mail]
> Cc: [e-mail]; Liang Xia <[e-mail]>; [e-mail]; IESG <[e-mail]>; [e-mail]
> Subject: Re: [Dots] Alissa Cooper's Discuss on draft-ietf-dots-signal-channel-31: (with DISCUSS and COMMENT)
> 
> 
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> 
> ________________________________
> Hi Med,
> 
> 
> On May 2, 2019, at 3:18 AM, [e-mail]<mailto:[e-mail]> wrote:
> 
> Hi Alissa,
> 
> Please see inline.
> 
> Cheers,
> Med
> 
> 
> -----Message d'origine-----
> De : Alissa Cooper via Datatracker [mailto:[e-mail]]
> Envoyé : jeudi 2 mai 2019 03:56
> À : The IESG
> Cc : [e-mail]<mailto:[e-mail]>; Liang Xia; dots-
> [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
> Objet : Alissa Cooper's Discuss on draft-ietf-dots-signal-channel-31: (with
> DISCUSS and COMMENT)
> 
> Alissa Cooper has entered the following ballot position for
> draft-ietf-dots-signal-channel-31: Discuss
> 
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> 
> 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-dots-signal-channel/
> 
> 
> 
> ----------------------------------------------------------------------
> DISCUSS:
> ----------------------------------------------------------------------
> 
> = Section 3 =
> 
> "By default, a DOTS signal channel MUST run over port number TBD as
>   defined in Section 9.1, for both UDP and TCP, unless the DOTS server
>   has a mutual agreement with its DOTS clients to use a different port
>   number.  DOTS clients MAY alternatively support means to dynamically
>   discover the ports used by their DOTS servers (e.g.,
>   [I-D.boucadair-dots-server-discovery])."
> 
> MUST implies an absolute requirement, so "MUST .... unless" is a problematic
> construction.
> 
> [Med] It seems that you missed "By default, “.
> 
> Even with “by default” this still is problematic. MUST indicates an absolute requirement.
> 
> [TR] “MUST (NOT)..unless” construction is used in several specifications, please see https://tools.ietf.org/html/rfc8094#section-3.1 and https://tools.ietf.org/html/rfc7232#section-2.2.1

Alissa is correct that MUST is absolute within the realm that it applies
to, so we need to be clear about what domain the requirement applies to.
The text in the -31 here is particularly problematic because of the
following "MAY alternatively" which is in a different sentence and has a
confusing relationship to the previous text.  A (hopefully clearer)
proposal:

In some cases, a DOTS client and server may have mutual agreement to use a
specific port number, such as by explicit configuration or dynamic
discovery [I-D.boucadair-dots-server-discvory].  Absent such mutual
agreement, the DOTS signal channel MUST run over port number TBD as defined
in Section 9.1, for both UDP and TCP.

-Ben