Re: [Dtls-iot] Spencer Dawkins' Yes on draft-ietf-dice-profile-16: (with COMMENT)

Spencer Dawkins at IETF <spencerdawkins.ietf@gmail.com> Thu, 01 October 2015 04:02 UTC

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Date: Wed, 30 Sep 2015 23:02:42 -0500
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From: Spencer Dawkins at IETF <spencerdawkins.ietf@gmail.com>
To: "FOSSATI, Thomas (Thomas)" <thomas.fossati@alcatel-lucent.com>
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Subject: Re: [Dtls-iot] Spencer Dawkins' Yes on draft-ietf-dice-profile-16: (with COMMENT)
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Hi, Thomas,

On Wed, Sep 30, 2015 at 4:28 PM, FOSSATI, Thomas (Thomas) <
thomas.fossati@alcatel-lucent.com>; wrote:

> Hi Spencer,
>
> Thanks for your comments.  Quick reply on this one:
>
> On 30/09/2015 19:04, "dtls-iot on behalf of Spencer Dawkins"
> <dtls-iot-bounces@ietf.org on behalf of spencerdawkins.ietf@gmail.com>;
> wrote:
> >
> >In this text,
> >
> >   On the other hand, the way DTLS handles
> >   retransmission, which is per-flight instead of per-segment, tends to
> >   interact poorly with low bandwidth networks.
> >
> >I'm assuming you are using "per-flight" in the
> >https://tools.ietf.org/html/rfc5681 sense of the term ("FLIGHT SIZE: The
> >amount of data that has been sent but not yet cumulatively
> >acknowledged"), but that's somewhat obscure, especially outside of TSV,
> >and there's no definition or reference for it in this document. Perhaps
> >you could say something like
> >
> >   On the other hand, DTLS handles loss by retransmitting the
> >   entire amount of data that has been sent but has not been
> >   cumulatively acknowledged, and this tends to
> >   interact poorly with low bandwidth networks.
>
> The term "flight" has a precise connotation in DTSL (see
> https://tools.ietf.org/html/rfc6347#section-4.2.4) which is what we imply
> here.


I learn something on almost every telechat. This is what I learned for the
current telechat cycle. Thanks for cluing me in!


> In the paragraph just above the one you've quoted, we reference section
> 4.2.4 of RFC 6347 which is where the term is originally introduced; so,
> although implicitly, we provide the context.
>
> I agree this is not perfect, but it's not easy to guess what the reader
> knows already, what his/her mental filters are, etc, so I'm not sure what
> we could do to make the text better/unambiguous?
>
> Cheers, t
>

(At a comment level), this (excellent) document includes an introduction to
(D)TLS in section 3, so I'm assuming that at least some of your intended
readers won't have more clue about DTLS flights than I do. Perhaps
something like

"On the other hand, DTLS handles loss by retransmitting an entire flight
(as defined in section 4.2.4 of RFC 6347), and retransmitting all
unacknowledged segments tends to interact poorly with low bandwidth
networks."

But, your call. Your least clued readers may be more clued than I am :-)

Spencer