[asterisk-users] Re: Help - Poor Voice Quality

[Ed W]

Hi

> Yes, I know that I am using IAX2 and not SIP for my connection to 
> teliax.  IAX2 is the preferred protocol for connection to teliax.  I 
> have the firewall configured to prioritorize port 4569 for IAX2.


1) 4569 is only the IAX setup port.  Edit rtp.conf to limit the rtp 
ports to some subset and then prioritise those instead
2) Uplink bandwidth is always the constraint on these lines.  This is 
highlighted in this case
3) Shorewall can't correctly prioritise bandwidth whenever using some 
kind of DSL service or whenever the packets are encapsulated such as the 
cable service.  Read the linux QOS faq for more info and as a workaround 
slash the theoretical bandwidth in half in your shaping script.  This 
should get you working and you can tweak later
4) Monitor the QOS buckets as you make/break calls to check that all the 
packets are classified correctly.  Otherwise your voip packets might be 
accidently in the bulk box

Basically VOIP goes from perfect to horrible when the jitter rises and 
packet loss goes up.  Probably this is happening in your case

Good luck

Ed W