Date: Mon, 05 Oct 2009 15:20:58 +0500 From: rihad <rihad@mail.ru> To: Eugene Grosbein <eugen@kuzbass.ru> Cc: freebsd-net@freebsd.org, Luigi Rizzo <rizzo@iet.unipi.it> Subject: Re: dummynet dropping too many packets Message-ID: <4AC9C88A.5050509@mail.ru> In-Reply-To: <20091005100532.GC73335@svzserv.kemerovo.su> References: <4AC8A76B.3050502@mail.ru> <20091005025521.GA52702@svzserv.kemerovo.su> <20091005061025.GB55845@onelab2.iet.unipi.it> <4AC9B400.9020400@mail.ru> <20091005090102.GA70430@svzserv.kemerovo.su> <4AC9BC5A.50902@mail.ru> <20091005095600.GA73335@svzserv.kemerovo.su> <20091005100446.GA60244@onelab2.iet.unipi.it> <20091005100532.GC73335@svzserv.kemerovo.su>
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Eugene Grosbein wrote: > On Mon, Oct 05, 2009 at 12:04:46PM +0200, Luigi Rizzo wrote: > >>> The goal is to make sources of traffic to slow down, this is the only >>> way to descrease drops - any finite queue may be overhelmed with traffic. >>> Taildrop does not really help with this. GRED does much better. >> i think the first problem here is figure out _why_ we have >> the drops, as the original poster said that queues are configured >> with a very large amount of buffer (and i think there is a >> misconfiguration somewhere because the mbuf stats do not make >> sense) > > That may be very simple, f.e. wide uplink channel and policy that > dictates slower client speeds. Any taildrop queue would drop lots > of packets. > If uplink is e.g. 100 mbit/s, but data is fed to client by dummynet at 1 mbit/s, doesn't the _client's_ TCP software know to slow things down to not overwhelm 1 mbit/s? Where has TCP slow-start gone? My router box isn't some application proxy that starts downloading at full 100 mbit/s thus quickly filling client's 1 mbit/s link. It's just a router. Although it doesn't yet make sense to me, I'll try going to GRED soon.
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