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Date:      Mon, 15 Oct 2001 20:44:24 -0700 (PDT)
From:      Archie Cobbs <archie@dellroad.org>
To:        Mike Tancsa <mike@sentex.net>
Cc:        freebsd-net@FreeBSD.ORG
Subject:   Re: strange results with increased   net.inet.ip.intr_queue_maxlen (solved)
Message-ID:  <200110160344.f9G3iOd33944@arch20m.dellroad.org>
In-Reply-To: <el0nst0h6lu5ndsioa7o5p2fhuu4tg8c9a@4ax.com> "from Mike Tancsa at Oct 15, 2001 08:52:55 pm"

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Mike Tancsa writes:
> >> Is it better for the networking layer to deal with this (potentially 
> >> introducing some latency) as opposed to letting the application ?
> >
> >But no, the network should just do "best effort".. that is, unless
> >you are a telco type in which case, go back to your X.25 :-) This
> >is a religious issue to some degree, but in practice the war is over
> >and the Internet won (vs. the telco way of doing things).
> 
> Thanks for the info.  Lugi Rizzo was kind enough to figure out what has
> been going on. I increased the queue size to 512 on both my OC-3 equipped
> machine (via the en device) as well as my pure FastE (via fxp) machines and
> the problems have gone away. As to why this solved the problem Lugi wrote,
> 
> --------------
> oh, did you see drops go to 0 when the queue size is 256 ? I missed
> this.  Then it means another thing, you are receiving a very large
> burst of packet from the interface, larger than ipintrq, and this
> is why they get dropped.

This makes sense.. and that's is exactly what queues are for:
absorbing bursts. If you have big bursts then you'll need big
queues.. in general this is the only reason to have them.

-Archie

__________________________________________________________________________
Archie Cobbs     *     Packet Design     *     http://www.packetdesign.com

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