From: Eric Dumazet <eric.dumazet@gmail.com>
To: Josh Hunt <johunt@akamai.com>, netdev@vger.kernel.org
Cc: davem@davemloft.net, edumazet@google.com, ncardwell@google.com
Subject: Re: [PATCH v2 1/2] tcp: add new tcp_mtu_probe_floor sysctl
Date: Thu, 8 Aug 2019 08:12:44 +0200 [thread overview]
Message-ID: <a3a69a9d-5e30-77c4-02e2-c644bfdab820@gmail.com> (raw)
In-Reply-To: <1565221950-1376-1-git-send-email-johunt@akamai.com>
On 8/8/19 1:52 AM, Josh Hunt wrote:
> The current implementation of TCP MTU probing can considerably
> underestimate the MTU on lossy connections allowing the MSS to get down to
> 48. We have found that in almost all of these cases on our networks these
> paths can handle much larger MTUs meaning the connections are being
> artificially limited. Even though TCP MTU probing can raise the MSS back up
> we have seen this not to be the case causing connections to be "stuck" with
> an MSS of 48 when heavy loss is present.
>
> Prior to pushing out this change we could not keep TCP MTU probing enabled
> b/c of the above reasons. Now with a reasonble floor set we've had it
> enabled for the past 6 months.
I am still sad to see you do not share what is a reasonable value and let
everybody guess.
It seems to be a top-secret value.
>
> The new sysctl will still default to TCP_MIN_SND_MSS (48), but gives
> administrators the ability to control the floor of MSS probing.
>
> Signed-off-by: Josh Hunt <johunt@akamai.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
next prev parent reply other threads:[~2019-08-08 6:12 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-07 23:52 [PATCH v2 1/2] tcp: add new tcp_mtu_probe_floor sysctl Josh Hunt
2019-08-07 23:52 ` [PATCH v2 2/2] tcp: Update TCP_BASE_MSS comment Josh Hunt
2019-08-08 6:13 ` Eric Dumazet
2019-08-08 11:58 ` Neal Cardwell
2019-08-09 18:38 ` Josh Hunt
2019-08-09 18:43 ` David Miller
2019-08-09 18:43 ` Josh Hunt
2019-08-09 19:59 ` David Miller
2019-08-08 6:12 ` Eric Dumazet [this message]
2019-08-08 15:14 ` [PATCH v2 1/2] tcp: add new tcp_mtu_probe_floor sysctl Josh Hunt
2019-08-08 12:02 ` Neal Cardwell
2019-08-09 19:59 ` David Miller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=a3a69a9d-5e30-77c4-02e2-c644bfdab820@gmail.com \
--to=eric.dumazet@gmail.com \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=johunt@akamai.com \
--cc=ncardwell@google.com \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).