Date: Tue, 13 Jan 1998 09:12:36 -0500 From: Brian McGovern <bmcgover@cisco.com> To: dwhite@resnet.uoregon.edu Cc: questions@FreeBSD.ORG Subject: Re: Re: PP degrades with file type on NULL modem Message-ID: <199801131412.JAA16981@bmcgover-pc.cisco.com>
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>> I was just running some tests on pppd here, between two Pentium Pro 200s >> connected via NULL-modem cable (via 16550). >> >> I ran pppd with -bsdcomp, crtscts, at 115200 baud. > >[...] > >> Anyone care explain to me why, when compression should not be involved, that > ^^^^^^^^^^^ > >> I can't get throughput that collates with bps rate (ie - if I can get 10.72 >> at 115200, why can't the other two files even come close?)? I just find >> it an oddity I'd like to have an explanation for :) >Did you disable *ALL* compression, including pred1 & VJ header? -vj -bsdcomp. I don't think pred1 shows up until 3.0. >Were both machines completely unloaded? Yes. Other than the normal system processes (I did similar testing with a boot floppy that just ran pppd and ftp, and similar results were noted). Both systems were hovering at about 99.9% idle (ie - an occational blip from top). >Were they both running FreeBSD? Yes, 2.2.5 (Release, not stable). >Nobody said ppp was perfect ;-) Did you try usermode ppp for comparison? Oh, I know ppp isn't perfect. I was just hoping it'd be constant. You should see what happens when you put v.42 modems in to the mix, and compression REALLY takes over. Highs of over 11K/s (which exceed the NULL modem speed for the same file - go figure), lows of 4K/s, all based on which file it is, the direction (ie - if I plug in a Cisco router at the other end, sending data to the router and getting data from the router have about a 4K/s difference). No, I haven't stabbed at the heart of usermode ppp yet. We run a lot of tests against our routers using a couple of platforms, and we're trying to make it as uniform as possible. Anyhow, if you have any thoughts.... :)
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