netdev - Re: [PATCH net-next] tcp: Add TCP

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Message-ID: <CAKfDRXh92_3H+8bJ7ieTeYVN7xNHhOzd8YvKZk9N0-_SwusgOA@mail.gmail.com>
Date:	Sat, 25 Oct 2014 23:21:48 +0200
From:	Kristian Evensen <kristian.evensen@...il.com>
To:	Yuchung Cheng <ycheng@...gle.com>
Cc:	Hagen Paul Pfeifer <hagen@...u.net>,
	David Miller <davem@...emloft.net>,
	Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] tcp: Add TCP_FREEZE socket option

Hi,

Sorry for my late reply.

On Fri, Oct 24, 2014 at 4:58 PM, Yuchung Cheng <ycheng@...gle.com> wrote:
> Do packets actually get dropped during the handover period? if not
> then the sender can detect spurious RTOs and undo the cwnd reductions
> with timestamps or DSACKs (Eifel). Eifel did not exist when the
> freeze-TCP was published at 2000. Even if the connection does not
> support these options as major TCP stacks do, slow-start on a path
> with new BDP isn't that bad of an idea.

Yes, there is 100% is packet loss when several of these handovers
occur. In addition to looking at the pcap-files, I have made some
tests were I send UDP traffic at the same time as TCP. The UDP traffic
does, as expected, resume as soon as the handover is over. The TCP
traffic, on the other hand, recovers when the RTO expires.

Thanks for reminding me about Eifel btw.

-Kristian
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