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Date:      Fri, 26 Apr 2002 23:11:40 -0700
From:      "Sameer R. Manek" <manek@ghur.net>
To:        <freebsd-stable@freebsd.org>
Subject:   PPP under 4.5-stable
Message-ID:  <LMEMIKHGPPEEMMMMGIENGECMEGAA.manek@ghur.net>

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Has anyone else seen excessively high latency across a modem based PPP link?
I have I have noticed that pings to the upstream router goes into the 6000ms
range. This is especially when I'm downloading something in another window,
or viewing an image intensive webpage.

I have tried altering the MTU of the tun0 interface, a long with adding this
to ppp.conf:
	set mtu 1000

But it doesn't seem to have any noticeable effect on the latency shown
below.
I don't think this is an issue with line noise, as i don't notice the
conditions associated with retraining modems. This also seems to have been
introduced after i upgraded to 4.5. I also didn't notice this problem when
this same system was running 4.4-stable

--- 209.239.192.11 ping statistics ---
115 packets transmitted, 111 packets received, 3% packet loss
round-trip min/avg/max/stddev = 1370.107/6053.621/8329.974/1492.298 ms

I have also noticed that during periods of "high traffic", about 6000cps,
the load average kicks up to close to 1, though it's certainly not using cpu
much, so it's probably a reflection of fact that ppp sits in the run queue,
an io-wait state.

last pid: 92042;  load averages:  0.81,  0.76,  0.67    up 5+05:36:20
23:06:48
45 processes:  2 running, 42 sleeping, 1 stopped
CPU states:  1.6% user,  0.0% nice,  0.0% system,  0.0% interrupt, 98.4%
idle
Mem: 46M Active, 433M Inact, 77M Wired, 37M Cache, 73M Buf, 33M Free
Swap: 1265M Total, 1265M Free

  PID USERNAME  PRI NICE  SIZE    RES STATE    TIME   WCPU    CPU COMMAND
92042 manek      28   0  1988K  1204K RUN      0:00  1.07%  0.63% top
86648 root        2   0  2540K  1684K select   2:58  0.10%  0.10% ppp


Sameer

-------------------------------------------------------------------------
Sameer R. Manek                                   Email: manek@ghur.net
"What one has not experienced, one will never understand in print."
 --Isadora Duncan
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