Re: [tcpm] 793bis: TCP Quiet Time

Neal Cardwell <> Thu, 19 December 2019 04:16 UTC

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From: Neal Cardwell <>
Date: Wed, 18 Dec 2019 23:16:14 -0500
Message-ID: <>
To: Yuchung Cheng <>
Cc: Wesley Eddy <>, "" <>
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Subject: Re: [tcpm] 793bis: TCP Quiet Time
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On Wed, Dec 18, 2019 at 8:28 PM Yuchung Cheng
<> wrote:
> On Wed, Dec 18, 2019 at 1:33 PM Wesley Eddy <> wrote:
> >
> > I don't think I noticed anyone responding to Gorry's comment below, and
> > I haven't made any alterations in the 793bis draft with regard to this
> > (other than fixing some spelling mistakes).  I wanted to pull this into
> > its own thread in case other people have thoughts or would like to
> > discuss further what the quiet time concept's relevance is in 2020.
> I probably am missing something. What's the issue of the text? Linux
> to my knowledge does
> not implement this quiet time.
> But there are other injection attacks or basic checksum issues etc to
> corrupt TCP. (Serious) application that solely relying on TCP's
> integrity is signing up for troubles already ...

I would agree with Yuchung's remarks and the general point that the
"TCP Quiet Time Concept" from RFC 793 does not seem to be of practical
importance today, from a number of perspectives:

o I'm not aware of any major TCP implementation that actually follows
the "TCP Quiet Time" approach.

o Most production applications AFAIK end up using SO_REUSEADDR,
indicating a need to reuse ports quickly and a lack of concern about
this kind of issue with old packets ending up mixed into new

o Applications that care about this should be using cryptography.

o Users today expect to be able to reboot a machine and get back on
the network in less than 2 minutes.