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Date: Sat, 10 May 2008 23:33:56 -0700
From: Julian Elischer <julian@elischer.org>
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To: Bakul Shah <bakul@bitblocks.com>
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Cc: freebsd-current@freebsd.org
Subject: Re: tcp over slow links broken?
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Bakul Shah wrote:
> Sometime during the past month or so, tcp out over a slow
> links seems to be broken and the symptom is really puzzling
> to me!  Here is my setup:
> 
>     A----B----DSL ~ ~ ~ ... ~ ~ DSL----C
> 

[...]

> 
> I looked through tcp related changes nn the sys commitlogs.
> There are a lot of them lately....  However, this comment in
> a checkin of 20008-4-17 21:38:18 UTC worries me :-)
> 
>   This change should introduce (ideally) little functional change.
>   However, it lays the groundwork for significantly increased
>   parallelism in the TCP/IP code.
> 
> Trace 1
> -------

> 14:22:42.317406 IP B.55535 > C.ssh: . 4744:6204(1460) ack 2016 win 65535
> 14:22:42.317489 IP B.55535 > C.ssh: . 6204:7664(1460) ack 2016 win 65535
> 14:22:42.410739 IP C.ssh > B.55535: . ack 4744 win 64240
> 14:22:42.411144 IP B.55535 > C.ssh: . 7664:9124(1460) ack 2016 win 65535
> 14:22:42.411259 IP B.55535 > C.ssh: . 9124:10584(1460) ack 2016 win 65535
> 14:22:42.468350 IP C.ssh > B.55535: . ack 4744 win 65535
> 14:22:42.490556 IP C.ssh > B.55535: . ack 4744 win 65535


that is just plain  wierd...  B seems to have gone deaf.

> 14:22:42.830171 IP B.55535 > C.ssh: . 4744:6204(1460) ack 2016 win 65535
> 14:22:43.470135 IP B.55535 > C.ssh: . 4744:6204(1460) ack 2016 win 65535
> 14:22:44.549944 IP B.55535 > C.ssh: . 4744:6204(1460) ack 2016 win 65535
> 14:22:46.509750 IP B.55535 > C.ssh: . 4744:6204(1460) ack 2016 win 65535
> 14:22:50.229210 IP B.55535 > C.ssh: . 4744:6204(1460) ack 2016 win 65535

have you made a kernel from each side of that commit and compared them?

>