Performance

[Ed Clarke]

> hey guys, 
> is ping a good way to determine connectivity problems??  
usually.  

> for example,, when i ping my home linux box through the cable modem.
> it has 38% to 50% packet losses, intermittently througout the day
> but if i ping my neighbor's windows95 computer through his cable modem, i 
> get 0% packet loss from the SAME source...........which leads me to 
> believe either my cable 
> modem is bad, or my linux box and card or is ping something that works 
> different with linux and/or windows?
Works the same.

What's not the same is your environment.  I spend some of my time keeping
a cable modem system up and running.  Is your neighbor on the same cable
amplifier that you are on?  That eliminates half of the problem ( the
cable system itself ).  If so then the signal at the modem may be too
low for some reason - crappy splitters for example.  If you bought a
splitter at Radio Shack, it may not pass back the low return channels
( < 40 MHZ ) without serious degradation.  Your modem may be turned down
for some reason too.  I can set power output for our modems remotely and
so can your cable system.  Call them; they can run remote diagnostics on
your system and fix the problem remotely if it's not a hardware problem
inside your house.  If you've added splitters, you may have cut the signal
level down too far for good connectivity on the receive side.

A current example:

.nodeRemod.nrMonitor.nrMonitorNoiseLevel = -26
.nodeRemod.nrMonitor.nrMonitorPowerLevel.0 = 10

The noise figure on the system at this time is -26 (no particular units)
and my power level is 10dbmv.  I check the modems on the system and raise
and lower their outputs to keep the same return signal level at the
node remodulator for all modems.  That way someone with a hot modem doesn't
kill someone with a low output modem due to AGC.

If the noise figure drops below -24, then there's a problem with the trunk
line somewhere (on THIS system).  This could be caused by lots of things -
some turkey with an illegal CB amplifier causing ingress to the cable return,
a bad return amp etc. etc. etc.  Or you could have a bad modem ... 8-)