Re: [Tsv-art] Tsvart last call review of draft-ietf-core-echo-request-tag-11

"Christian M. Amsüss" <> Wed, 09 December 2020 15:09 UTC

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Date: Wed, 9 Dec 2020 16:09:00 +0100
From: Christian =?iso-8859-1?B?TS4gQW1z/HNz?= <>
To: Joerg Ott <>
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Subject: Re: [Tsv-art] Tsvart last call review of draft-ietf-core-echo-request-tag-11
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Hello Jörg,

Thank you for your review and your comments.

> One question that arises is why these three quite distinct mechanisms fixing
> different parts of the RFC 7252 are compiled into a single document. Efficiency,
> yes, but otherwise, they don't seem to have much in common.

The mechanisms also share common patterns in the attacks they prevent,
and playing through scenarios of one mechsnism led to a better
understanding of the others. It is hoped that the reader can use the
mind set built up understanding the necessity for one mechanism leads to
a better one on the others.

> A question out of curiosity: in section 3.4, could a client easily exhaust server
> resources if just sent many blocks and changed the Request-Tag on each of them?

No more than it can by addressing them to different resources (where the
query parameter is part of the underlying identity) -- or even any
made-up uncritical safe-to-forward option. CoAP servers that perform
atomic processing typically have limited slots for these operations
(either global, per resource or per client), and any later request
invalidates the former's state.

> Should sections 3.6 and 3.7 move to an appendix? They discuss design alternatives.

Question for these came up so frequently in discussions around the
document that I think it's better here where it's visible.

Happy to move it over if you or other commenters insist, but that should
happen in awareness of the underlying questions' occurrence.

> The last sentence in the second to last paragraph of section 1.1 has nested brackets,
> which may or may not be intentional.

It's an unintentional occurrence which I'd -- now aware -- also make
consciously to avoid extra prose that'd set aside the defining terms
from the accompanying remarks.

The remaining nits have been addressed in the editors' copy, and will be
part of the next version.

Thanks again

You don't become great by trying to be great. You become great by
wanting to do something, and then doing it so hard that you become great
in the process.
  -- Marie Curie (as quoted by Randall Munroe)