Date: Tue, 21 Jun 2005 07:52:47 -0700 From: Luigi Rizzo <rizzo@icir.org> To: Pieter de Boer <pieter@thedarkside.nl> Cc: freebsd-net@freebsd.org Subject: Re: Issues with a Large Fat pipe Network simulation Message-ID: <20050621075247.D63359@xorpc.icir.org> In-Reply-To: <42B731CD.1040104@thedarkside.nl>; from pieter@thedarkside.nl on Mon, Jun 20, 2005 at 11:14:53PM %2B0200 References: <42B722EF.2090203@thedarkside.nl> <20050620135044.B35720@xorpc.icir.org> <42B731CD.1040104@thedarkside.nl>
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On Mon, Jun 20, 2005 at 11:14:53PM +0200, Pieter de Boer wrote: > Luigi Rizzo wrote: ... > However.. when I deleted the pipe rules on 'network', the speed suddenly > went up to around 800mbit/s too! I remade them, and voila, 200mbit/s. network emulation is a tricky job :) in any case i believe what happens is the following. The pipe has a default size of 50 slots, which at 1500 bytes is little above 64k. If the sender is bursting a large number of packets, it may well overflow the pipe's queue causing a backoff (which may simply be immediate, or delayed, depending on how you configure various things). I believe setting the queue size in the pipe to a value larger than the window should fix things. can you confirm that ? cheers luigi > So apparantly it's an issue in the dummynet configuration I have. So, to > reiterate: > > On 'network': > pipe 1 from client to server via em0 > pipe 2 from server to client via em1 > allow ip from any to any i am > Will give me 200MBit/s when using 128KB window sizes, but 800MBit/s when > using 64KB window sizes. > > On 'network': > allow ip from any to any > > Will give me 800Mbit/s when using 64KB or 128KB window sizes. I haven't > configured the pipes in any way, though. > > > So it appears it's due to the 'network' box afterall.. > > -- > Pieter
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