T. Shaw wrote:
Hello all,
I have a problem with call quality with my Asterisk setup. I'm doing
VOIP only so far, but have a zaptel TDM400P in the box not being used.
The problem i'm having is that when calls are placed, connected, and the
far-end is reporting that they are experiencing clipping, choppy, and
garbled voice conversations. So bad that we have to resort to using our
cell phones. This entire setup is still being built, but any phone
attached is experiencing this. Call volume is almost nil (under 20 total
incoming calls a day). This is a small business setup. The server is
used exclusively for Asterisk, so it isn't a fileserver, or anything else.
The setup is as such:
ipphone <--->cisco 2900XL switch <----> Cisco 2621 router <---> dsl
modem <-->DSL <---> VOIPprovider
I've configured the switch and the router to set priority and qos to
prioritize voice traffic above data.
Funny thing is, there is not data REALLY hitting the network. I have
setup 2 vlans, data vlan, and voice vlan. There are two work stations on
the network, and neither is being used to hit the internet heavily
(office is still being setup).
Any pointers or suggestions anyone have for me as to were to look for
this poor quality?
It seems only the Far-end (called party), is hearing this and not the
calling party.
I haven't tried switching out the phones because we only have 1 type,
and any of the phones i used exhibit these problems. I will try
softphones to see if it is truly a "networking" issue or Phone issue.
Is anyone using a cisco 2900 switch or router and care to provide config
samples of their COS/QOS setup?
Highly unlikely the ipphones or switch have anything to do with the
problem. Most likely cause is the dsl "upload" speed (which is usually
substantially slower then download speed).
Just as an FYI... the QoS settings in any Cisco product (including the
2900 switch) do not actually kick in "until" a switch port becomes
congested. So if your switch ports are running at only 10 megabits,
you'd have to be moving data (including voice) at that rate before QoS
begins to give priority to voice packets.
If your voip provider supports a low bit-rate codec, you might consider
using something like g729 to see if that impacts the problem. If it does
improve it, then either your dsl connection is the problem (to slow),
or, your dsl provider's data network is less then adequate to move the
voice packets through in a reliable way.
There are several internet sites that you can use to test your bandwidth
if you want to try those. One is dslreports.com, but there are others.
Goggle should give you plenty to work with.
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