[Cerowrt-devel] [Bloat] TCP TFO client behaviour

Ketan Kulkarni ketkulka at gmail.com
Wed Dec 12 04:01:13 EST 2012

On Tue, Dec 11, 2012 at 11:22 PM, Dave Taht <dave.taht at gmail.com> wrote:
>> I really wonder why this is sent to these lists instead of netdev ?
> In my case I find it impossible to read netdev on a regular basis,
> with the size of the traffic and the unbelievable patch burden - (not
> that I can't filter it, but that fairly often I find a patch too
> tempting to not apply and then play with)
> I have no problem taking a conversation to netdev if needed...
Well, I have opened a thread on netdev as well.

> However I'd note that TCP fast open is not just a linux feature, but
> affects the entire internet. Perhaps the readership here has a more
> broad view of how this should be approached.
First, I would really like to get wider views about this.
My only concern is -
If syn+data is sent by client and syn-ack only acks the ISN, then isnt
this a sufficient indication that server now is not supporting the
So for further connections to this server instead of sending syn+data,
only ask for cookie. (fall back to the state where it was all started)
(Note that this condition is different from syn+data is dropped in the nw.)

Yuchung might be right in saying it doesn't lead to any performance
penalty, however sending syn+data to a server seems a little odd when
we know we have sufficient information to believe that it may not be
accepted at first, retransmitted later. And otherwise we also have a
way to fall back and re-attempt the TFO.

If you guys still insist, I can stop here and continue on netdev.

> Ketan has been busily adding support for TFO to a couple tools used in
> cerowrt. (httping is already out there in a release!)
> It's my hope to be able to sanely test it in cerowrt's 3.7.x release.
> I also am concerned about TFO wider adoption into other tools like
> these (ssh? dns?) and what those effects might be.
> I'm probably dropping the syn optimization in simple_qos.sh because of
> tcp fast open. But I would prefer to gather data and test, first, with
> good tools. Are there any other tools besides chrome and httpping
> setup for clients?
> I look forward to trying out the polipo support.
>> _______________________________________________
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>> Bloat at lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/bloat
> --
> Dave Täht
> Fixing bufferbloat with cerowrt: http://www.teklibre.com/cerowrt/subscribe.html

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