Messages in this thread | | | Date | Sat, 8 May 1999 22:24:03 +0100 (GMT) | From | "Alex Butcher(linkern)" <> | Subject | Re: TCP/PPP latency |
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On Sat, 8 May 1999, Rik van Riel wrote:
> Hi, > > I'm experiencing _bad_ trouble with TCP/PPP latency lately. > > About half of my calls to demon.nl gives normal PPP latency > and performance (100 to 200 ms latency), but sometimes I get > a network latency of 20 to 30(!) seconds on the PPP link. > > I'm using kernel 2.2.7 with the following PPP command line: > > /usr/sbin/pppd lock modem /dev/modem 115200 idle 90 demand \ > defaultroute mru 296 mtu 296 bsdcomp 15,15 $LOCAL_IP:$REMOTE_IP\ > novj netmask $NETMASK connect $DIALER_SCRIPT > > Before switching off Von Jacobson compression the network > latency was usually worse, but now it's all right about > 50% of the time...
Have you recently started using Demon NL? I had similar problems with Demon UK until I disabled VJ header compression. Once I did that, the problems went away *completely*.
Some friends at a rival ISP reckon it's because the remote access servers Demon UK use run out of horsepower if they're fully utilised *and* people are using VJ. I have no evidence to back this up.
If this does turn out to be a Linux problem, I'd be very interested in testing any patches...
Also, Demon UK recommend a mru/mtu of 576 and they don't do BSD compression.
Finally, you might want to run your serial port at 230400bps if you have a >28.8kbps modem to take full advantage of the 4:1 compression your modem can perform. More details on www.tunelinux.com (incidentally, Rik, feel free to use my 'tuning PPP' doc there on your 'tuning Linux' site - I don't want you to feel left out! ;)
> Rik -- Open Source: you deserve to be in control of your data.
Best Regards, Alex.
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