[asterisk-users] Diagnosing poor call quality

[Chris Bagnall]

Greetings list,

We have an issue with call quality at 2 sites where the users (4 Elmeg
IP290s at one site, 2 SPA942s at the other) do not have an asterisk box
on-site. Each site has an 8mb down/448k up ADSL connection and the phones
connect via SIP to an asterisk box in a datacentre using g729.

The asterisk box in the datacentre connects to our other asterisk boxes
providing pstn connectivity via IAX2. Latency between these boxes is between
1 and 2ms. The ADSL connections to the client sites are all consistently
delivering latencies of sub-25ms to the datacentre and there is traffic
shaping on that connection to give priority to any traffic from the phones'
IPs.

Comments from the users at these sites are as follows:
"call sounded like a dalek and I couldn't make out anything the caller was
saying"
"the phone on my desk is breaking up so badly it's virtually unusable"
"calls sound like they're breaking up with metallic background noises"

We have quite a few customers with asterisk boxes on-site (with phones
connected to them via the LAN) using ADSL connections from the same
supplier, and are not having these issues with them.

canreinvite=no and nat=yes are set on all these devices, since they are
behind NAT. Each device re-registers with asterisk every 5 minutes to
prevent any possible NAT state timeouts.

Any pointers/places to look for potential problems would be much
appreciated.

Regards,

Chris
-- 
C.M. Bagnall, Director, Minotaur I.T. Limited
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