iperf is great. Another essential troubleshooting tool is nfsen/nfdump
(or any netflow/sflow monitoring utility that shows DSCP/TOS tag values).
On 10/28/2013 01:55 PM, Mike wrote:
As stated in previous replies if you haven't already I would certainly
try to isolate the problem, e.g., are extension to extension calls
good, is the problem only on outside calls etc.
We are starting our 4th year of VoIP service and have had two
seemingly similar episodes to yours during that time. We are on a
non-symmetric cable connection, 20/4 (I believe). After a few days of
"crappy" audio I started looking for some way to
characterize/correlate bad audio with something I could measure. I
found iperf (http://iperf.sourceforge.net/) to be a free and easy
starting point, which actually turned out to be all I needed.
I simply ran a "server" instance on our "cloud" server roughly 1K
miles away and a "client" instance locally. I used the command line
swithces that forced udp mode. This allowed me to see jitter and
packet loss in both directions. We had terrible packet loss in the
outbound direction. This didn't show up in normal browsing, emailing
etc., kinds of things as I suspect TCP retries masked the problem.
With a little persistence with the cable company the second tech found
a bad "tap" (I believe) outside at the cable drop. Replacing that
solved our issue for almost two years.
The next time this happened iperf showed a similar packet loss
problem. This time it turned out to be "noise in the system" according
to the cable tech. He said it could be from any number of sources but
a different team would be out to hunt it down the next day. In the
mean time he changed out our old Moto SB5101 modem for a more modern
DOCSIS 3.0 modem. The multiple channel bonding that it offered was
much better at punching through the noise. That change alone ended
crappy audio as well as packet loss as shown by iperf.
--
--
Jules Agee
Senior System Administrator
Pacific Coast Feather Co.
jul...@pcf.com x284
--
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