[asterisk-users] Diagnosing dropped calls...

[John Faubion]

> -----Original Message-----
> Subject: [asterisk-users] Diagnosing dropped calls...
> 
> 	I have a system that is driving me nuts.  My customer 
> is running Asterisk 1.4.20.1 on a CentOS 5.2 server.  It is a 
> purely SIP and IAX2 service with no cards installed and it 
> uses ztdummy from Zaptel 1.4.11.
> They use Teliax for calls to the USA and Protel for calls in Mexico.
> 
> 	The problem is that users complain that their calls get dropped.
> Sometimes every few minutes and sometimes after a very long 
> call over two hours so there is no clear pattern.  There is a 

I just went through this same scenario. The customer originally using Teliax
over AT&T DSL. Incoming calls would sometimes have a delay of 1-2 seconds
before connecting and some would just drop at random intervals. We would
generally see in the logs that our connection to Teliax would often show
lagged or unresponsive around the time of the drops. Testing with AT&T
revealed that the customer was 18,034 feet from the CO so we decided to move
them to a cable modem from Charter. This was done as it was the only other
internet provider short of a dedicated T1. Things improved but did not
completely subside. The delay on answering was becoming the major complaint.
We decided to try a different provider so an account with Junction Networks
was added. This eliminated the delay immediately but did not eliminate the
dropped calls. One of the techs at Teliax told us that the delay was an
issue caused by Asterisk 1.4 trying to talk with Asterisk 1.4 server. We
tried their work around but it did not eliminate the delay issue though it
did reduce the issue. We also had Charter monitor the service for nearly two
weeks in which time they replaced the modem 4 times and claimed to have
repaired connectors, replaced repeater nodes and changed other connections
to no avail. The customer lives and dies by their telephone so we moved them
to Cbeyond SIP Connect. All of the issues are now gone. The is no delay,
they some times spend hours at a time on training calls with no issues. I
also did a bit of testing with the Junction Network account after moving to
Cbeyond. This was done since we still had money in the account anyway. Again
no more issues with dropped calls. The key is in an Internet connection that
is either very clean or supports QoS. The Cbeyond connection seems to have
both. Obviously we don't have QoS back to Junction but with the cleaner
connection it doesn't seem to matter. Also if you trying to use a cable
modem, make sure your using a business class service and not a residential
service. 

Also use mtr (mytraceroute) to look at the latency between your server and
the proxy. Under Charter and AT&T, both of which were business class
services, the mtr would sometimes show up to 20% packet loss at various
systems between us and the proxy. Also try different proxies. For us the
best one was typically either Atlanta or Denver. Keep in mind that I'm not
bashing Teliax or Junction. I use both Teliax at home and Junction in our
office, over a cable modem provided by Time Warner and the only issue I have
is the occasional delay on answer with Teliax. However that one is the home
line and the delay seems to work great for telemarketers. 

John