Messages in this thread | | | Date | Mon, 28 Feb 2011 16:51:29 -0500 | Subject | Re: txqueuelen has wrong units; should be time | From | John Heffner <> |
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Right... while I generally agree that a fixed-length drop-tail queue isn't optimal, isn't this problem what the various AQM schemes try to solve?
-John
On Mon, Feb 28, 2011 at 12:20 PM, Bill Sommerfeld <wsommerfeld@google.com> wrote: > On Mon, Feb 28, 2011 at 07:38, Hagen Paul Pfeifer <hagen@jauu.net> wrote: >> On Sun, 27 Feb 2011 18:33:39 -0500, Albert Cahalan wrote: >>> I suppose there is a need to allow at least 2 packets despite any >>> time limits, so that it remains possible to use a traditional modem >>> even if a huge packet takes several seconds to send. >> >> That is a good point! We talk about as we may know every use case of >> Linux. But this is not true at all. One of my customer for example operates >> the Linux network stack functionality on top of a proprietary MAC/Driver >> where the current packet queue characteristic is just fine. The >> time-drop-approach is unsuitable because the bandwidth can vary in a small >> amount of time over a great range (0 till max. bandwidth). A sufficient >> buffering shows up superior in this environment (only IPv{4,6}/UDP). > > The tension is between the average queue length and the maximum amount > of buffering needed. Fixed-sized tail-drop queues -- either long, or > short -- are not ideal. > > My understanding is that the best practice here is that you need > (bandwidth * path delay) buffering to be available to absorb bursts > and avoid drops, but you also need to use queue management algorithms > with ECN or random drop to keep the *average* queue length short; > unfortunately, researchers are still arguing about the details of the > second part... > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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