Subject: Re: [core] Murray Kucherawy's No Objection on draft-ietf-core-echo-request-tag-12: (with COMMENT)

From: Christian Amsüss <[email-masked]>
Date: Sun, 18 Jul 2021 22:41:44 +0200

Hello Murray,

thanks for your input on echo-request-tag, and apologies for the delay
in processing them to completion.

Please see [1] for a few general comments; here's the response to your
particular comments:

> There are several SHOULDs (e.g., near the top of page 8, and again at
> the end of Section 2.3) that left me wondering why an implementer
> would do something other than what it says.  Since SHOULD offers a
> choice, some advice would be helpful here.  Otherwise, maybe those
> ought to be MUSTs.  I suggest giving them all a once-over to see if
> any such advice would be helpful to include.

Some categories of SHOULDs were identified that did not warrant any
additions:

* "You can do it differently and it wouldn't be wrong just weird (but
  maybe you have good reasons we don't understand)": eg. 'MUST NOT
  process [...] further and SHOULD send a 4.01 Unauthorized'. If the
  application has a successful code in a content format that indicates
  "try again with whatever I'm providing you here", that's technically
  fine and won't break things (which'd justify a MUST). But it's not
  like we can give good reasons to do that other than "someone decided
  to do it differently in that API", so there's nothing good to say.

* "If you have anything better, be my guest": In some places, there is
  no current alternative but no reason to rule them out either. It's
  unlikely there'll be an "Echo 2.0" that does the same just different,
  but a more complex mechanism that provides freshness as bycatch would
  be a viable option in some places.

For others (eg. SHOULD use preemptive values, pointing to privacy
considerations), options were given; one SHOULD is indeed a MUST
(HTTP-to-CoAP proxies) as there's no other viable option.

Best regards
Christian

[1]: https://mailarchive.ietf.org/arch/msg/core/SIHjiM5AjFRZJRZGUjf3cW1sUu4

-- 
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