[Asterisk-Users] Garbled voice on long distance calls

[matt.riddell at sineapps.com]

On 20 Sep 2004 at 10:50, Devon Stephens wrote:

> I do know what QOS is, and the effect it can have on VOIP, although
> I'm no expert on QOS.  However, I assume that our Packet 8 phone would
> be having the same problems at the same time as *, unless Packet 8 is
> doing something to compensate for packet drops, or jitter that *
> doesn't do. 

The only thing I can think of here is Packet Loss Concealment, which 
is built into some codecs but not yet included in Asterisk.  There 
are developers interested in this, but it would be a major change and 
definitely won't happen till at least after 1.0

>I did set tos=lowdelay, but that will only help if the
> routers between me and Nufone honor the request. I don't really know
> enough about QOS to monitor it if it's not on my own network though. 
> I'll look more into that.

It's unlikely to be running without you setting it up.  There is a 
good resource on the wiki at:

http://www.voip-info.org/tiki-index.php?page=QoS

It really makes a big difference when you download a 100Mb file at 
the same time as multiple voice calls.  TC will put any packets with 
the flag you set (i.e. tos=lowdelay) into the first bin and the rest 
of the traffic should fall into the later bins.  You can also set it 
up so that any traffic coming from asterisk ports/ip is put into the 
first bin.  TC will then only send the latter bins if the first bin 
is empty.  Because your voip traffic is not using the full bandwidth, 
there will be times when the first bin is empty and TC will send the 
contents of bin 2 etc.

Don't forget to set your maximum connection speeds to be slightly 
lower than your actual maximum so as to stop your ISP from buffering 
the data.

Cheers,

Matt Riddell
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