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Re: [TLS] Efficiency of ACKing scheme

Eric Rescorla <ekr@rtfm.com> Thu, 09 April 2020 14:18 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Thu, 09 Apr 2020 07:17:27 -0700
Message-ID: <CABcZeBN=jsr-WJnbxNao+jLneEGz8waTkGerHqexKVekBV-aug@mail.gmail.com>
To: Thomas Fossati <Thomas.Fossati@arm.com>
Cc: Hanno Becker <Hanno.Becker@arm.com>, Rob Sayre <sayrer@gmail.com>, "tls@ietf.org" <tls@ietf.org>
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Subject: Re: [TLS] Efficiency of ACKing scheme
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On Thu, Apr 9, 2020 at 6:59 AM Thomas Fossati <Thomas.Fossati@arm.com>
wrote:

> On 09/04/2020, 14:20, "Eric Rescorla" <ekr@rtfm.com> wrote:
> > Assuming I understand Hanno's proposal, I do not believe that this is
> > in fact an improvement, as it does not cover the important case where
> > the record containing the SH is lost and then the rest of the messages
> > from the server are uninterpretable.
>
> I don't want to speak for Hanno here but the refinement proposed in [1],
> specifically the bit that says:
>
>   [...] They may also proactively retransmit parts of a flight early if
>   an ACK message indicates a gap.
>
> should cover the case you mention I think.
>

But this requires being able to send an empty ACK that means "I got
nothing". In which case, I don't see how it's really different from the
current text except that it gives the sender less guidance.

-Ekr

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