Date: Sat, 26 Jul 2003 01:13:49 -0700 From: Luigi Rizzo <rizzo@icir.org> To: freebsd-ipfw@freebsd.org Subject: Re: using dummynet to simulate modem, dsl, etc Message-ID: <20030726011349.A60140@xorpc.icir.org> In-Reply-To: <20030725114822.A2287@cs.ucsd.edu>; from ycheng@cs.ucsd.edu on Fri, Jul 25, 2003 at 11:48:22AM -0700 References: <3F212BF7.4060602@optusnet.com.au> <20030725103814.A54554@xorpc.icir.org> <20030725114822.A2287@cs.ucsd.edu>
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On Fri, Jul 25, 2003 at 11:48:22AM -0700, Yuchung Cheng wrote: > On 07-25-2003, Luigi Rizzo wrote: > > I would expect you to get around 3.5KBytes/s in the steady state, > > but with a packet transmission time of 200ms and the 600ms RTT of > > your setting, the first few rounds might achieve somewhere between > > that and twice the bandwidth because of less interference. > > > > This is exactly what you are seeing. > > > > Try this: > > ipfw -q add 1 pipe 1 ip from any to 127.0.0.100 in > > ipfw -q add 2 pipe 2 ip from 127.0.0.100 to any in > > ipfw -q pipe 1 config bw 33kbit/s queue 0 delay 40ms > > ipfw -q pipe 2 config bw 56kbit/s queue 0 delay 112ms > > > why set queue to 0? aren't modem banks usually 4K bytes? the reverse link > has 3 times delay (c->s), is this for simulating ack spacing and busy > server to client pipe? i just copied those parameters from the original posters. I have no idea on what system he had in mind. In terms of delay, i typically used to see some 120-150mss RTT for short pings (including everything). Just the transmission time is in the order of 5-10ms at each step, and there are many instances of it (serial->modem; modem->modem; modem->serial on the remote side; and another 3 on the way back) so i think this eats almost half ot the total delay. In terms of buffering, again i have no idea, but at least on the client side you have as much as the local OS gives you. cheers luigi > I am doing similar experiments. Anybody can share parameters for ADSL, cable > modems too? Searching the web does not give any good information. > > Yu-chung > _______________________________________________ > freebsd-ipfw@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-ipfw > To unsubscribe, send any mail to "freebsd-ipfw-unsubscribe@freebsd.org"
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