Re: [tcpm] 793bis: TCP Quiet Time

Matt Mathis <> Thu, 23 January 2020 06:59 UTC

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From: Matt Mathis <>
Date: Wed, 22 Jan 2020 22:59:06 -0800
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To: Joe Touch <>
Cc: Fernando Gont <>, "" <>
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Subject: Re: [tcpm] 793bis: TCP Quiet Time
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There are two other changes that have largely made this problem moot:
a) ISS and ephemeral port randomization make it extremely unlikely that
segments delayed across a reboot will be in sequence for any connections
(at the time this was written, both ISS and ephemeral ports were generated
by counters starting from fixed integers).
b) Although not reflected in policy, the effective MSL of the internet has
been declining as it gets faster.   There are paths and devices that can
delay packets by more than 10 seconds but they don't normally cause packets
to be reordered by that much, so a new SYN can't pass an old data segment,
which is a requirement for triggering the hazard.

I would suggest changing the text to say "a theoretical problem....  that
could be fixed by...  but for the following reasons it is viewed as being
sufficiently unlikely to ignore.

The best way to predict the future is to create it.  - Alan Kay

We must not tolerate intolerance;
       however our response must be carefully measured:
            too strong would be hypocritical and risks spiraling out of
            too weak risks being mistaken for tacit approval.

On Wed, Jan 22, 2020 at 10:27 PM Joe Touch <> wrote:

> On Jan 22, 2020, at 10:54 AM, Fernando Gont <> wrote:
> On 8/28/2019 11:39 AM, Gorry Fairhurst wrote:
> OLD, Section: "   The TCP Quiet Time Concept"
> - Found this section quite amusing. Is this concept widely implemented in
> stacks?
> No.
> It might be useful to consider this is relevant only for systems that
> reboot in under 2 MSL anyway. That’s a good reason most systems don’t need
> to care - but a good reason to worry about ignoring this issue as we move
> forward.
> I.e., of this concept and its utility, as financial investors advise:
> Past performance is not be a predictor of future results.
> Joe
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