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Date:      Sun, 7 Jul 2002 10:31:49 -0600
From:      "John Nielsen" <hackers@jnielsen.net>
To:        "John Kozubik" <john@kozubik.com>, <freebsd-hackers@FreeBSD.ORG>
Subject:   Re: multi-link 802.11b through netgraph yields poor performance.
Message-ID:  <00ea01c225d3$cbac0250$0900a8c0@max>
References:  <Pine.BSF.4.21.0207070053570.40375-100000@www>

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John Kozubik wrote:
> Julian, Archie, et al,
>
> I have experimented with a multi-link 802.11b connection between two
> laptops.  Both are 4.5-RELEASE, one has two aironet LMC352 cards, and
> one has two Lucent gold cards.
>
> I have successfully used ng_one2many, etc., to establish a working
> multi-link between the two systems - however, I would appreciate any
> comments regarding the very poor performance I see when networked in
> this manner.
>
> The problem I see is that, when using `ping` on either machine,
> exactly every other packet is dropped.  After running `ping` for many
> minutes, trying it from both machines, it is clear that _exactly_
> every other packet is dropped.  Further, echo response time is
> between 2.2 and 2.5 milliseconds, which seems very high.
<snip>
> Any comments as to why the problems I am seeing (half of packets
> dropped and high latency) exist are appreciated.

I am using a multilink connection between a fileserver and a switch, and it
works fine.  This is with regular 100Mbit ethernet cards.  On one occasion I
unplugged the "secondary" NIC from the switch without undoing the one2many
setup.  And every other packet to the machine was dropped.  I saw the same
thing you were seeing with your pings.

So.. I would think that netgraph is doing its thing, distributing packets
evenly between your two interfaces, but that one of the interfaces isn't
behaving.  My one2many script is essentially the same as yours except for
the order.  I don't know if it makes a difference (it _shouldn't_), but in
my script I bring the secondary interface up before doing anything else (and
then I load the ng_ether and ng_one2many modules, but I assume you're doing
that elsewhere).

I don't know a great deal about any of this, but I thought this might give
you a clue as to what to look for.

Good luck,

JN


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