[asterisk-users] Audio problems on cable modem link

[Joel Maslak]

On Fri, Oct 15, 2010 at 8:53 AM, Michelle Dupuis <mdupuis at ocg.ca> wrote:

When a single call is up, call quality is fine.  When a second call is up,
> outbound audio is immediately choppy.  We're using ulaw, and confirmed that
> traffic with 2 calls is <175kbps in/out.  (IAX connection out)
>
> Asterisk doesn't report any dropped frames, the internet connection looks
> fine, etc.   We have a linux router in place running wondershaper that seems
> to be running fine (same as our other installations).
>
> Can someone suggest where to look?  Could this be the ITSP?
>


It could be your traffic shapper, the ITSP, your local network, the ISP's
network, or the internet backbone - basically anywhere in-between.

You only have control over your local network, so I'd start there.  Look for
duplex mismatches (hint: if one end is set to "auto" or not able to be set
manually, the other end should also be auto, never full [don't worry,
they'll negotiate full, but only if both ends are set to auto; otherwise,
the auto end will negotiate half due to the end running full not
broadcasting capabilities when hardset]).

That said, I've never felt great about using the internet for phone calls -
you can't controll anything else in the chain, so the possibility of
problems is huge - and most of the time you can't fix it.  I know lots of
people here do it, but it's going to be problematic.  If you want
toll-quality voice, you still need either TDM lines or dedicated
(non-internet) bandwidth.
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