> 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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