Date: Fri, 30 Nov 2001 16:03:55 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Alfred Perlstein <bright@mu.org> Cc: Jonathan Lemon <jlemon@flugsvamp.com>, Nate Williams <nate@yogotech.com>, Alexander Haderer <alexander.haderer@charite.de>, jlemon@freebsd.org, freebsd-hackers@freebsd.org Subject: Re: Found the problem, w/patch (was Re: FreeBSD performing worse than Linux?) Message-ID: <200112010003.fB103tF27870@apollo.backplane.com> References: <20011128153817.T61580@monorchid.lemis.com> <15364.38174.938500.946169@caddis.yogotech.com> <20011128104629.A43642@walton.maths.tcd.ie> <5.1.0.14.1.20011130181236.00a80160@postamt1.charite.de> <200111302047.fAUKlT811090@apollo.backplane.com> <200111302130.fAULUU324648@apollo.backplane.com> <15367.64883.390696.863120@caddis.yogotech.com> <200111302200.fAUM0hD27448@apollo.backplane.com> <20011130162832.N46769@elvis.mu.org> <20011130165747.I75389@prism.flugsvamp.com> <20011130170811.S46769@elvis.mu.org>
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:what should happen is this:
:
:h1 send: p1 p2 p3
:h2 recv: p1 p3
:
:h1 recv: (nothing acks lost)
:h2 send: ack1 ack1 ack1 (dude, i missed a packet)
:
:h2 send: ack1 ack1 ack1 (dude, i missed a packet)
:h1 recv: ack1 ack1 ack1
:h1 send: p2 p3
:
:Basically, will the reciever keep acking not if 'it detects packet loss',
:but rather 'as long as packets are lost'.
:
:--
:-Alfred Perlstein [alfred@freebsd.org]
Yuch. That won't help. Basically you are taking a brute-force
approach "Send the ack a whole bunch of times in case some of them
get lost". Such an approach does not typically work very well. For
example, if the packet loss occured due to link congestion your
solution will actually make the link more congested rather then less.
If there is significant latency in the path the acks can get into
a following run with the transmitter, making the transmitter believe
that the packet loss is worse then it actually is and responding in kind,
resulting in even more incorrect acks.
-Matt
Matthew Dillon
<dillon@backplane.com>
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