[Asterisk-Users] need help troubleshooting clipping and garbledVOIP calls

[Philippe Lindheimer]

Interesting web tool, but the results are completely misleading and wrong on my system that I just tested it on 5-6 times. And this is a connection that I use regularly for VoIP traffic, multiple channels (although just a few) and I am very familiar with the characteristics of the internet paths to various providers and other trunks I am connected to. So ... from at least one datapoint, doesn't seem reliable.

As far as the QoS issue - there are some reasonable links on the wiki that describe some techniques you can use with the Cisco box and you will also want to investigate if there are issues between you and your provider. Usually though - the issues are at the edge.

Oh - and if Asterisk isn't running as root, the ToS settings won't happen for the outbound packets. (In case you are using that for your ACLs on Cisco for QoS rules). There is a patch that I have never tried. I find it simpler to just use iptables and create a few simple rules to set the ToS for outbound packets based on SIP/IAX and RTP ports per your configuration.

philippe

From: "James Hawks" <james.hawks at customerfunding.com>
To: "'Asterisk Users Mailing List - Non-Commercial Discussion'"
 <asterisk-users at lists.digium.com>
Date: Thu, 29 Jun 2006 13:39:28 -0700
Subject: RE: [Asterisk-Users] need help troubleshooting clipping and
 garbledVOIP calls

 Sounds like a QoS issue with your DSL provider. If you go to
http://www.bandwidth.com/tools/voipTest it might give you some insight.

James Hawks

-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of T. Shaw
Sent: Thursday, June 29, 2006 1:27 PM
To: asterisk-users at lists.digium.com
Subject: [Asterisk-Users] need help troubleshooting clipping and garbledVOIP
calls

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?

Thanks!

Terrelle Shaw


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