Messages in this thread | | | Subject | Re: TCP Stalls. | From | Mark Gray <> | Date | 02 Sep 1998 06:10:28 -0400 |
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"Richard B. Johnson" <root@chaos.analogic.com> writes:
> > On Wed, 2 Sep 1998, Alan Cox wrote: > > > > If I corrupt loopback so it fails to transmit a few packets, I can > > > emulate the same kind of TCP stalls that have frequented the kernel. > > > > I'd expect exactly what you describe. TCP cannot cope with loss above > > 1 frame per pipe length without seriois performance loss. Typically thats > > 5-10% loss. Above that it will back off a lot. > > > > Your model is then flawed because the back off doesnt induce lower error > > rates through reduced congestion. You model a continuous 25% loss link > > layer - and that is something that unaided is beyond the capabilities > > of an IP network. > > > > Alan > > > > Okay. That's good. This might point to a serious problem with the PPP > link (losing lots of packets), because that's where the bad stalls occur. > > I can run serial I/O to serial I/O (regular 'C' programs in Linux) between > two computers with two modems _and_ the phone line with only an occasional > lost character (actually a group of 6), far less than 1/2 percent. Maybe > flow-control isn't working in PPP??
Try using a smaller window for ppp (works for me.)
My ppp startup script executes the following after bringing up ppp:
/sbin/route del default dev ppp0 /sbin/route add default window 16384 dev ppp0
Without it, certain files are impossible to download from some ISP's; with it, I have no problems whatsoever. (This is with only 2.0.* -- there is too much I need to use that is still broken on 2.1.* so I have not tried it yet (although I did notice that there was talk of a major change in the Window code.))
(Just a possibly off-topic comment from the peanut gallery -- gentle flames only please.)
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