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Re: [L4s-discuss] Entering CWR state during the loss recovery algorithm (NewReno, SACK)

Neal Cardwell <ncardwell@google.com> Wed, 20 December 2023 16:57 UTC

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From: Neal Cardwell <ncardwell@google.com>
Date: Wed, 20 Dec 2023 11:57:28 -0500
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To: Francis Rammeloo <francis.rammeloo@gmail.com>
Cc: l4s-discuss@ietf.org
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Subject: Re: [L4s-discuss] Entering CWR state during the loss recovery algorithm (NewReno, SACK)
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Hi,

For context, can you please describe the transport
protocol, OS/library/implementation, congestion control algorithm, and ECN
flavor (RFC 3168 or L4S) you have in mind? I ask because most of these
behaviors you mention don't match the Linux TCP Prague behavior when using
L4S ECN (which I would imagine would be the default scenario discussed on
the l4s-discuss list, though perhaps not?).

best regards,
neal

On Wed, Dec 20, 2023 at 10:03 AM Francis Rammeloo <
francis.rammeloo@gmail.com> wrote:

> During loss recovery, the CWND is strictly managed by NewReno/SACK. For
> example NewReno "inflates" the CWND to allow sending new packets in
> response to duplicate acks and when the recovery is complete CWND is set to
> SSTHRESH. If CWR is entered during loss recovery then this could interfere
> with the loss recovery algorithm. Also when the loss recovery is complete
> it will set the CWND to SSTHRESH, so the reduction by CWR can become undone.
>
> Should entering CWR be "disabled" during loss recovery?
>
> Greetings,
> Francis
>
>
> --
> L4s-discuss mailing list
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