Date: Sun, 7 Jul 1996 19:43:40 -0700 (PDT) From: Jaye Mathisen <mrcpu@cdsnet.net> To: David Greenman <davidg@root.com> Cc: Network Coordinator <nc@ai.net>, freebsd-questions@freebsd.org Subject: Re: Increasing FTP thruput. Message-ID: <Pine.NEB.3.94.960707193833.26573A-100000@mail.cdsnet.net> In-Reply-To: <199607080147.SAA00690@root.com>
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All this might be true, but the article I sent a reference out about recently pointed out several shortcomings in TCP re slow speed links, and that tweaks that helped the high end were having a negative effect on the low end. Sun specifically rewrote the drivers and tweaked some constants to help with this specific issue, so it doesn't surprise me at all. My users see similar behaviour. They can FTP files faster from an unloaded NT box than they can from an unloaded FreeBSD box. yet both can drive the thernet at wire speeds. (They're coming in over a 28.8 PPP connections to Livingston PM's and Digiboards) In both cases the configs are almost identical, P120's, 3com ethernet, 2GB Seagate disks, NT3.51 on a Buslogic, and FreeBSd on and adaptec. This is reproducible at will. So now after I went to all the hassle to switch from BSD/OS to FreeBSD, I find I probably would be able to keep more users happier by changing things to NT. This is depressing. I have the original article still, if anybody is interested. On Sun, 7 Jul 1996, David Greenman wrote: > >On one of our development machines we are running wu-ftpd. When FTP'ing > >over a T-3 to a PPP (28.8kbaud) line from a PPro 200 to it we were seeing > >as low as 2.0k/second. Yet, FTP'ing from a Sun 4/75 we were seeing > >2.8kbaud solid performance. > > > >It appears to be [by watching modem lights] that the BSD box isn't > >streaming in the sense of a continuous send or receive while receiving > >acks along the way. The Sun boxes [all of them] seem to do this out of > >the box. > > > >I verified this behavior on ftp.cdrom.com and random SunOS boxes. > > > >Any ideas how to make the BSD behavior more like the SunOS? > > Watching modem lights is an extremely poor way to do critical analysis. The > SunOS machines send out ACKs every other packet and further restrict the > window size to 4096 bytes. I'm really suprised that FreeBSD comes out worse > in your test. If you're doing the tests using ftp.cdrom.com as the endpoint > then you might be seeing the effects of asymetric lossage - especially since > there are so many intermediate hops involved. I suggest looking for dropped > packets in the netstat -s statistics. > Oh, and you didn't mention which version of FreeBSD you're using or whether > you're using the kernel PPP or usermode ijppp. You could be seeing the effects > of one or more bugs in the PPP code. > > -DG > > David Greenman > Core-team/Principal Architect, The FreeBSD Project >
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